Stretch and challenge quesrions are indicared throughour the Studencs Book with thefollowing icon @.These questions are aimcd to r,.-.,.h and challenge all srudents by usingdiilcrent assessment suaregies including: a varicty "r;r;;,;;;;;;;:;;:;;;;;:_1.rr.orvriring opportuniries and diffcrcnt question nro", ,o enabre studenrs to deverop and use a'varicry ofskills.All srudcnts shourd bc abre to give anslvers ro frcse quesrions and a basicansrver 'is oudined belor.v for each of them, However it is expected rhat candidates workingat higher grades wi'givc a grcarcr dcpr'ofanswcr bri'ging in cxrcndcti knowleclge andundersranding from a variety of sourccs,

pages 1G-11

I Marks arvarded for: Most imporrrnt rc:ic,ion because armost r,' lire on earrh dcpenc:on it' only Iarge scare rvay in which new organic morecu-les arc synrhesised in livingorganisms and the oniy rvay in rvhich a ncw supply of ATp can bc builr up. any oL..vaiid point.

Marks not awarded ror: without respiradon, celrs dic so phorosynthesis can,t take place.wirhout slnthesis of proteins, tl-rcrc is no AT'pase, so no ATp cycle. Almost impossible torank reacdons in terms of importancc. Any orher valid point.2 a Releases energy rvhen AT? broken down to ADp in a form available to alr ce, enzymes.ADP and inorganic phosphatc can be rcrorrned inro A r-p by AT1)ase usirg energy iiomuniversal reacdons, suclL as rcdox reactions, rri'Jrin rhc cer1. A^ny orher valid poinrs.

b Evidcnce to incrudc: prescncc in'a, ccr-l rlpcs invcsrigatcd, prcscncc in every speciesinvesrigated, impacr on ceus if ,{fp synthcsis o. br.r-k,ro*r-, in}ribited. Any other valid point.

pages 1 2-1 3

l'l a Bccause not a' rhc cclrs carry out phorosynt'esis - any parrs or.rhc prant which are_-...

not direcdy exposed to light wil) nor conrain chlorophyll.'b..lFolded membranes givc Iarge surface area.

Enzymes on mcmbrancS rnd in sUoma Lo crrr), out rcactions.Pr6sence of severar photosynrhetic pigments to absorb difrcrcnt waverengths of light,Any other valid point.

2 Noneofthepigmcnrsabsorbwcti'thcgrccn/yclrorvrrcirsofthcspcc*um,AsrJrisrightis not absorbed, it is reflectcd rvhich is,,vhy plants appcar green_

Ipages 14-17

Cyclic photophosphorylation Non-cyclic photophosphorylation

involves PSI and p5ll

electrons ccfie froffi and retuin tochlorophyLl in p5l

NADP recuced to reduced NAD during the process

etectrons lost on excitation from the chlorophylt molecutes inPSli are replaced by electrons from the cx riation of *.t..- '

no reduced N,.,D produced as

electrons return to chtorophyll

ATB reduced NAD and orygen formed

Edexccl A2 B'olo8y Implcmcnradon and Asscssmcnt Guide rorTeichcrs and'r'echnicirns gpcarson Educarion Limircd 2oo9

arcasl

6 refcrencc to moniloring ovcr time;

rcicrcncc [o non-functioning of s}'napscs / cq;

conuol of {moror functions / motor ncurone lunction};

reicrcncc to {cercbcllunr f nlotor cortcx / parictal lobc};

rcference to substantia nigra / basai ganglion / mid brain); (2)

dopamine cannot cnter rhc brain / L-dopa can be convcrted ro dopamine/

L-dopa is {casicr / cheapcr} to make / conversel (1)

1 tNtRI / FMRI) scan / {C'f / CAT} scan / thermal imaging /X-ravs / PET;

2 rcfcrcncc to 3-D imagc; [only apphcs to Ml{I' I;MI{i' CAT scan and P}iT']

3 {shrpe / sizc / colour} Jiflcrcncc;

4 densitY of ussuc;

5 comparison to image of a normal brain / mcthod of identification of damaged

(3)

lTotat 6 Qarks]

Edcrccl A2 Biology Irnplcmentaoon and Assessment Guide for Tcachers and Technicirns oPearson Educrrion Limitcd 2009

3 ln a biochcmical process that depends on or is alfectcd by a number of factors' the

process rvill bc }imitccl by tlrc factor that is ncarcst to its minimum value'

Thc amounr of light availablc alfccrs dlc amount of chiorophyll drat can be excitcd and

drereforcthcamountofrcducedNADandADPproducedinthelight-dependentstage.If*rcrersaiorvlcvcloflighttlrcninsufficicntrcduccc]NAl)andATPwillbeproducedtoallorv the reacdons of rJ-rc light-indcpcnccnt stagc to progrcss at thek maximum rate , so

light is the lirnitir-rg factor.

Low levels of carbon dioxidc available for fixing in rhe Calvin cycle means that the

rcacrions.rnnnt prn.."d irI drc miximu.r ratc]Whcn this is thc casc) carbon dioxidc is

rhe limrting factor. In rhe natural sirualion of plants it is mosr often carbon dioxide that is

the hmiting factor'

All of rhc calvin cyclc rceirior.ls and many of thc light-dcpcndcnt rcacdons of

phoLosynthcsis arc controllccl by cnzyncs anrl ate drcrcforc scnsitive to tcmpelature.This

mcans rhat. cvcn whcn t1-rc light and clrbon dioxidc lcvcls arc suitablc for a very high rate

of phorosynthesis, if the lcmperaturc is low, thc plant will be unable to take advantage of

thc condirions.

w_A? Biology lmplcmentation and Assessmcnt Guidc forTcachers aDdTcchnicians OPcarsoo Edustion Limircd 2009

'/ fhc habirar is the ,addres

ttrortr[s shou]d ot "tt''o"t^ol

l'c organjsm - it dcscribc

Thc nichc <iescribes *" 'o'."'n "'-top;"l ';;;;':];:'

tt'hcrc it livcs' suirable examples of

. rnhabit rhe same nro,,r, l,l].. o[ an rnimrr .'r,u'',,;;;;,'""tt

a lu; (mrnv oLhcr possibi.rires).

Ln u'oodrand: ,op p..6.,"b-titt'pv uiff.."n,';,.,*l'olt" - so sevcral organisms may

squrrrer, crc. rr fox, primarv ..;;;;;.;;r;::t:,n ir' For cxrmplc, rood njchcs, _"riuq,/rcr raDDltr hrEe rree_dweJjlng herbivore

-2' Full dera:ls shoLrld bc givcn of u,h;.,L^.._ , .Iink hcru.ccn ,,lro;;;^":"

of.whichcvcr biomes choscn. A crcar undersr,.r;*^s and ric '""0';;;, ;;;ii^'"li ^'''"1'understanding ortire

pages 2o-23 ur ulc llsbltal shc'rrld bc shown,

pages 1B_i 9

pH of the soil

J Thc proccss by rvh.icare rcplaced b,

",n..l:Tuniljcs c'rf rnjrnals arr.

*r...T.-#J"ffi "#:f;.;;n1;,."jff f$ilti:::*il:f :ff;#::'-.

r"2 A communiry reached ., ,t " ".u ";" "..-""":-ly

tre scme urrir condirions change again.consisr of t,],re ,r,n. a",1-ul

thc, en'l of r serics of sr

communiries. planrandr",",r,.f....r.;.r:rilil::il::H:"::,;;,"

Ld Irrimary succe:sjon Icoloniscd by 1;;;::l

brre rock or sanJ dune

:) _ , rings bur rnor.i.,,.J.* ""''t'secotrdarl'succcssion on land tirar rvas

r_1, {.) tS+Cl The answcrs shoulcl jncjudc somc or all of

" t'l:i' sreadv growrh

'" "" ;;';;:j^:::t't'

rolJowing' odrer points may be varid.soil devetoped. Tr"i :tj: num-ber of spccics

r

d*'siepg6 ,r r.. r,fl a period

"tr'r*"*i*'i"as condidons changcd and nrore

rrrey broughr ".* ;l:::.:'o

*i'n"",;;;;;,ii 10""' t nt4-e0 as drc isrrnd had

droppings n"O ,o .j_tlltt on lheir b",ii;r';;;;,"'

tcrultrv' Oncc bircls colonissd j51sn.s

b some rp..r.,,rt.h,il^'lo" "to'';;';;;ril*"'ed rerriJicv of rle soil with rheir

r brceding poprrrri^i:t:.tlc isl:rnd

'nd ,,rr, ,o;tttut"o

again reladvely rapidly'

r-hc island., oin r.l,l,oiplanrs So .;;';;.::"*t:"

but crnnot survivc to establish

cumuJaLive ro..,"r," rimcs than

"t" ";;r;i;;;: or l.isnrs lta'c bccn obscrvcd on

courd drop .",.,0.,i1,1.t n' '""',,.;;;;;'J;::::il:i,ilj;::.#i:r'.*j',",,,

c If rJrc prcdrcrrc_rrrs by s .

drop as row,, , o, *,Tl'li;:;l:Jil:i;:,1,1"-,::::l :: ::J

s; , ii, s couJcr evenruarJymOrenCwspcCiCSbecc_ ---'! rut.u wlll rcma

pases 24-22 :me cstabrishccr o"r;;;v:i,ffi::';J::::or1'rcn so up ir

1a -lhe non_livjng elemenrs of r

ll"^'; :l.. " i;; :il?J,* ;::;::: :,::l ln,.n

. pop u, a d on or organiliving. Dxrmprc, - .;':::i.T: environnrcnr iu which a pnu otrr'. roir. "-

:o rncludc unv or,.lo,.l;.,,::l;T:::j.ililj:::Ti; *. 1 ^, .

,-,Lr lsrcvant pOtntS sUclI y nolottc factors dctcrmir- ctc.rhis

'";;";..r;::,1,;]l','1""'t orrbe soir, rhc

which pranrs *',, o.li,'"',].i:l]"'"1"i" rvatcr avaitalririrycrc.Thjs in rurn decides *i,,:.'j,,,,,,,

ot rhe soil, rhc lcnli

:i1:.5;;'#.T#l:1il:H;l'ff j:i;';Jii::.::J"i:::'""1:':l'11.,in,rurn affecrs *. "*.. *ur"'r

ptants rvill be able to erorv ".d *.t".,. #Xi.'ltJril,,:oronisers

"r,",.;';;;,,:J|j:::,'",T:.::.bc abre ro surv,ve. rn rerms ortr. r.,i]

col oni s ers of a n a re a, r r,;;; ;;.;":r' rX'.. i.:irl

An1' 5ri1r61. cxamplcj sucir as in a wind1, en'ironmcnt watcr will evaporate from theground morc rapidll, 5e rvill bc lcss availabic ibr living organisms, high light lcvcls but lowoiygen levcls meitn many orgarrisms cannot grow rvcll and rcproduce etc.

Any suitablc examples dcmonsuadng an understanding of how the animal/plant isadapted to the panicular abioric factor sclecrcd.

pages 28-29

I Is+c] 'lhe answcrs should includc somc or all olr]rc following. other points may bevalid.

Any rhrce suitable cxamplcs, including one bird anri onc mammal, with clear explanationofhorv tcrritorics arc markcd and defcndcd, e.g. scinr marking, physical displav/dance,fighring.

y \vith liule biodiversity, if onc organism is alfccted by discasc it will have a major in"rpac.on the small numbcr of otl.rer organisms in the ccosystcm - rhcy won,t gct eaten or tleirprey numbers will fall subsranrjaliy.\Xuirl lrttlc biodiveLsiLy rJrere will bc fcw other availablefood resourccs. Also discasc is ntore likr:ly to sprcad benvccn inciividuals where there arefcrv bulfer spccies. In a more di'crsc communiry, changcs ciue to disease are lilely rohavc lcss of an cilccr as rhcrc is much more varicry of food choice and more buffcringorganisms to prcvcnt sprcad o[ discasc.

pages 30-33

1 inrraspccific - bctwccn mcmbcrs of the samc spc:ics, c.g. for territory, mares, food.I^raspccilrc compcritior tc'cls to affcct drc rb'.<rrncc of r particular spccics oforganism - lorv rcsources, rnuch compcutron, less reproduction and more mortaliry -numbe r dccrease. Plenty of resourccs - littlc coinpctirion, Iors of breeding, Iorv mortality,numbers increase.

interspccific - bctwccn mcrnbcrs ol diflcrcnt spccics, c.g. for space, food.Interspecific - this lcnds to affcct the diitriburion of spccics in a habitat and also theabundancc of spccics - thc biodivcrsity. If onc spccics comperes very successfully againstothcrs, it wi'll tcnd to drive thcm to extinction in thc arca.

2 [s+c] Thc ansrvcrs shourd rncludc somc or an of thc foilowing. orher poinrs may bevrlid.

a Adding food - hare dcnsiry more dran rriplcd.Excluding predarors - hare dcnsity more rhan doublcd.Ferrilising d.ie grass had no major effcct.Adding food anri rcmoving prcdarors - harc clcr.rsir,v wcnl up by a facror of abour i5.

b Ifaddfood,haresbrce,rmorcsucccs:fulry,burmoreuiil arsohetakcnbypredarorswhich will also breed succcssfully. So rhc impacr olrhc lood on rhe hare popularion isnot luliy illustratcd in thc population numbers.

Edc\ccl 42 llioloS] Implemcntatioo an<l Asscssmenr cuide fol'ltachcrs and'ltclnicians ol'carson t.iucrtion Liriited 2009

Jlt;:* hare popurarion -**'se4eu****;"''**

#Jother racrors 0.r," ,.'*,1 l::l:::":.0." a resurt or L

;*:::,:4 o',..,"#*,ii', l"*.- iTl,. *.'-,1,i'i'"1;#,;ffiTiffnipuiadon,

ffi lTj T;:;; ",,n::

j: :,il:ff fi ,l.,ilili * : * : *o, i" u *, .,

,"JJ,i:;:i*lfii:TFl.ili?lllT;;T,".J*ji::,;:,::.fi :::::ff :a;,:::;: i'Jili;:;"T i: : il ff j:::'"il,3;:: : ::l a;;.' ;;il"';i "1

?. ""I

;::: :mltri;IT ii I ri t,tr r;H H I x i jl jrirfi i ll ;::T* :* i l;

"". ".,"- *:rr-,:rr.'nI)ensiry_indcpen denr f

.,"-R.., r,,. il; ;;..Jil:::::i,f 1",'hl, rlc disrribu

r io,: of r n^^;^

,^ffi tr *,iriilH?t x, :,r":,i, #*.:?Im ; r

.Densiry-dcpend.",;;;:-:" oecorncs densiry-depcnd.;

;;;::' no\v mush lishr, warer erc. is

;ili::: * ; . ;;; ; ; : J :.i,il.:lTff ,,l..:.ilffi il:: l::T : :::: :, : s o rvii ] cn d

Pages 34-37 - "*r vrvc rn a parLictrlar

I a Algac and coral rcrb opcn ".;;; ;;;:,11100r",-,u- proclucd

c .r rioush *., n. "." 11..'

p'od u'rion ;;,;" J;# j 1:,'1,::'-

t s urface

;, r,,, , r,;s.,i.;;, ,;::: procjucdviry

rrcrc is a

2 a proc,ucerJ," ,;;;:t'ct

on total o."ur.ur',, "" cnormous amount of opcn ocean so

'..m*",*iiffi:ffi::,,j:#b (r 6.7 . .., ;';,;rt consuners;

B.e%

' . anr r",*0,.**"".'

-.- 30 1/3 = 1o'o%

isn"'. ,r.r.,in;*":::l :' would be roo compric

. vu,er ccosysrcm,*o,jil rvirhin a "*,,1.1"*,,"r;:,':::::],""

as a food wcb, canb Any rcasonable

assLrmwirrrin biomass

"r,;;i,i.ll]:,:^.Juding using ,".,,r.';.:'j":'-o'*

*'* stucJics of

species which ".. ".i" ".i^",i..

spccics, qsLirnr,., "," u"o"iru,l11lll*i:iJii::::*transfer in,o u ,p..;., *".i. il:;:f.l in nurnber, ma.ng csrimrres or.n;#"r'n*

Pages 38-39

1 [s+c] The ansrvers should include some or all of the follorving. orher points may be

valid.

The link shouid bc made bctwecn releasing carbon from sinks more rapidly than normal

and morc rapidly $an photosynthcsis ctc' can removc it'

i'Z\ Ar-osohcre: increasing intjusUiaiisarion, clccUicity gencralion, cars and othcr road

'J ,.hi.l*, acroplanes, ali producrng carbon dioxide cmissions affect amount of carbon

dioxide in the armosPhere.

Soil organic mattcr: tcmpcrature (rate ol acriviry

any scnsiblc altcrnativc.

Occan: tcmperature) any sensiblc alternative'

o[ brcrkdorvn) dcath rate of organisms,

Nlarinescdimcrlts:c!osion)acidiryofrvater,acidrainctc.)anyscnsiblea.ltcrnadve.

Terresuiaiplants:seasonofthcycarintcmpcratcareashasabigefiectong}oba.lphotosynthcsis lcvcls, dcforcstation' crop growrh and harvcsting'

Pages 40-41

i'il p.opt" could stop eating becf and using tlairy producls, bccausc millions of people around

V ,r.," *orro reiy on mcat and miLk fiom ruminanrs as a major part of rheir dict and big

farmingintercs$havealotofeconomicc}outand*'ouldobjcct.Anyothervaiidpoint.

2[S+C]-l.ircanslvctsshouit]irrcludcson]eolallofl}rcfollolving'othcrporntsmaybevalid.

Thegreenhouseeffecrisvitaltomaintaintl]cSuIl.i]CeofthcEarthatatcmperatulesuitable for life. It is thc enhanccd grcenhousc cffccr, clue ro increasing levels of

greenhouse gases, that is potentially a problcm'

pages 42-45

t 20.81%; allow i9-21%

@ Carried out ovcr iong period of timc, r,ery large numbcr of rcadings, sanic or sinrilar

measuringequipmcnlusedlhroughout,areaoflolvairpollurionetc.ADyotherrelevant

Point'

y':', clives a much longcr timc pcrspccrivc (rcadings going back over a thousand years),

V .ho*,. narural falls and riscs in carbon dioxide concentrarion and events of last coupie

ofhundrcdycars.Anyclt-lrcrvaiidpoints.i{clirrbiliLy0.2ppnr.Corrciadonwilhothercvidencc.

€) ffr. data shorv rhar armosphcric carbon tlioxidc icvcls hlvc increEed.They do noi show

the sourcc of the carbon dioxidc'

A .i^--.^,:.r.,..^t\) a Jtuocnl s}rou}d questior-i validiry of c1ata, Staustical ncdrods used, inciusion of uce-

ring data in original'

b 200svcrsioncontainsalargcrnloulrtofcxtlrdttalronrhundrcdsofstudics,nvodiflerent starisrical methods used, figures calculated both wiih and rvithout uee ring

data. AnY othcr valid Point'

EdcxcelA2 lliology lmplcmenreuon rnd Asscssrncnt Cuirlc frrr'l'clchcrs rntll-cchniuirns C'Pcrrrorr i}lucrtion Limitcd 2009

tt.tpages 46_47

86'7%,70.7%- carbon dioxide frn* r^.-ir r.. , , --."^ -":"t" lrr tc^perature?

a E'idenco ^F ^^-^.. from lossil fuels has incrr:ased mote than other sources.a E'idence ofcarerur research rn.r .L:r:---.

' --u!q rl'1u1c uran otner sources.

tcrms orclrriry oridcas,::HlJ:i:l:::.::^'tn up rlrc rrrcnsrrrs and *cakncsscs interms of clarity of idcas, rcliability of tlara ctc.

l^:"0 a. closeness of dara, rvhich comes

::::" *: c",*;;;, ffi ;ffi:::ll T*: :: ::^?.1tf

,,"10..^,ure or possib,evalid points. validity and re Iiability of dam, Any other

1 Graph A shows glaciatior

;,'.'.'T.f tr;:*:J?:ffi ff :ffi,ill,,;i;lTililTJf ffill[ jff :Graph B shows close correlee'ets. which comcs firsr * .r#:: j::t"'.'*llru...: ,.-ogruture and carbon dioxidelcvcls.which .on-.., nrra--.il"ri

1lt Parlern beLwcen lemperature and carbon dioxi36.70/^ tn zot

langc in carbon dioxic.lc or change in rcnperature?

pages 4&51I Any va)id poinrs sucF

don'r know t;;;;i as; rmpossible to predicr ne

ci r i ve ro r e d u c e ".,

o "; ijj;;",'; ;; ffi ;' ; ":'#::-i::;*:"TJililii

".2 a 43y0,2.7yo

b t5Omm

c Increasing carbonenhanced ,...*o,1lo*t*

levels thought to cau

on mounrains, ,.r, ur" .T.,, ,"..".ri;;;;;;.use

.rise in global temperatures due ro

poies. This .rur", .l"1o.I ltrrl"g c"

" ?iffiututt'

causing melring of snow cover-lse ln average sea levels.

nperatures and mehing of snow at

i3) Parricul:rrlV affccts disr

"' ::TR:,T,1; j*i ##{r i:;:: l:::.:*J:i:d, o c,im a rc c,ranse - ri sins carbon

arc a s wh e r e * ", ;." ; ; :li*;; :T:,H i : i[,:.,

J, #il ;; :il:,""# l"4 Look for claricyof thought and understanding of rh,pages 52-53

--.'"lrurrrg or ure possible sequcnces ofevcnrs,

I Any valid poinrs here. h

ln*:T";* jt fli;;t if :]: T:;T " ;l"tl I_,*, I a, n. .n1b.dy can

though lhar invorves n","i^d,

ot]'utn* " *" 1""*tJl'on'nt

counries cannot strive

to be unpopura. ", "

n"r,lll in"'"""

'" ';;;:;;.i morc dcvclopcd counrics *'cn

rnevitably unpopuJar ", ,::.1t,::o '"0 t";,;;:;xrde

emissions' politicians don't rvant

2 IS+cr The answers ,n,n"

*0"' "" '"0'"li"'i.i:i.:':J::"::'-",'":icirv/peror

etc are

valid. -- - -"ourd includc some or ail of the fo.llowing. other points may beAnswer should cover rhcansrver, and

",,;.;;;#J;1,1,]tii;illJr',ll;.1i:*,,thar ,nereis no comprete

Edercel A2 Biology Implementation rnc

#e forTcachcrs and rechniqiaos opearson Educadon Limired 2009

Arges 54-55

( 1) I'rorcomicsistJrcstu.ll oIali rhcdiffcrcntJrrorcinsrharcanbcmadeasaresultof *iegenomc throughout thc lifc olan individual, at all tie diflcrcnt stages of developmcnt as

, a rcsult of differenriai gene expression. Should note that there are far more proteins thangcnes. Genomics is the srudy of thc DNA, thc se qucnce of drc gcnes and the specific

alleies in place in an individual.

y (.1) Diif.t.n, allelcs arisc as a rcsult oi'mutaiion - changcs in rhc scquence of DNA bases.'' Chunges in allcle frcqucncy in a populadon usually occur in rcsponse to enviror,,mental

changcs. lf a particuiar allclc or combination ol'rllclcs produccs a survival or rcproductivcadvantage for tle organisms rvhich havc thcm so thcir oflspring are more likely to survive

and brced again, the frequcncy of rhe allcle will increase (e.g. Malpeque oysters from AS

levei). Alternarively, if a particular ailele becomes disadvantageous, the frequency wiildccrease (c.g. Biston bcuilaria from AS lcvel).

pages 56-57

$/ In ordcr to plant the apple orchards huge areasrof natural bushes would have beenploughcd up.-lhis wouid have dcsrroycd many harvLhorns, tre natual habirat of the flies,

rvhich in turn would havc lcd to some fcmalcs bcing lcft rvith no alternative but the apple

uccs on rvhich to iay drcir cggs.Thcn some of tJrcsc flics would have had aileles whichhclpcd thcm rccognisc thc sccnL of thc appics, or digcsr applcs cffecuvely, or lay eggs ar

times that fit the pattern of apple uee llor,vering and fruiting ratler than hasthorns.Theseflies would be most likely'to survivc and pass on rheir alleles, thus changing the allele

lrcquency in rhe popularion and moving towards speciation.

2 Any suitable cxamples.

arges 58-59

* (!) tn ordcr to mcasurc gcncdc divcrsity, to idcnrify relationships berween d.rfferenr species,

ro uack the process ofcvolution, ro idenrify lraud in foodsruffs such as caviar, to idendfyways of conuolling discasc. Any orlicr suirable cxamplcs.

2 Ilecause thcy are prescnt in a rvidc rangc of different organisms, and so rhey can be

comparcd.The gcnes mutate a[ a measurable and suitabie rate, which al]ows the timesincc cven rclatively closcly rclatcd organisms shlrcd thc srmc gcncs to be calculated.

pages 60-61

f}) a Fossil evidcnce is limircd: only relarivcly small numbcrs of organisms are fossilised,V small nutnbcrs oIfossils arc found, fossils c,ltcn nor intrct.Thcre may also be

similaritics in anatomy duc to convcrgcnt cvolution. Any valid other point.

(9 ONa starls to dcgradc immcdiatcly aftcr dcadr so iimircd application. Mutarion rares

of diffcrent genes varies considerably so timing can be very diflerenr depending onwhich gene used.

c Evidence from any one source has limitadons and potcntial inaccuracies which reduceits validity. If evidence from different sources gives similar results, the more valid areany conclusions drawn. Similarly, using diflcrcnt sourccs can show up discrcpanciesand prcven! time and money being wasted on erroncous data. Any other valid point.

Edcxccl A2 BioloS-)_ lftPlcmenlatjon and Asscssment Cuidc for Teachcrs anilTcchniciins G)Pcarson Educrtion Liniled 2009

@ t t n a i The r ns rvcr s r.

--.***sa-msmrrtu'Liui.;;o#"***;gggi*

valid. ,. " "hould includc somc or all of drc loilorving. Orher points may beHelps to validate nerv rrsevcral reams ,r"0"..'ullilt-t

bv presenting ir to pe

rs confirmed. Anor", n.,:l,u:: ':'utt' in '.t.i*r;J:"" t?' conslrucdve criticism' when

cooperadvc rcsearch u.;1'ot" to bc aired

^t;^;;;;i"n'tle'aliditv of all their findings

c x ch a n g c ",

o, r* * ",, "

]I"l'o'"' " o ; ; ;; i,' JJil::"'-;t'; li ii1 iiii' ln "'ill'

l)isadven12gs5. prcssurc to nrrht;.r, .,,..r ..,lrive peoprJ ro ;il;"rJ:tlish

attd rppcar at co'fcr,runding sroups can .ourrh.l"

r}cv have;"*r;;;;';:t"t"'can skcw rescarch and

- ca'y rnor;ring ,.,n.r, o..,lll:pul"' p'p"... T,ilin-''rdara'

Vcsrcd interesrs and Jarqe

rhe accepred view can o. u.l.t'l:tt qer Bood .r;';;:;; ,'a'cr car) minimise audicnce

moders. peopre need ro be "o1tjl

n ""*ti,"-.*

**rtr'\cw tccas rvhich go agairrst

mi ri ga r es .*,,",,,.""i, * ; n:I;l;l; ;;#JJ.'.:,:':'J.::: ::: ::*il, ff

-

Edexcel A2 BioloEy Inplemenurr'on and Asscssment Guide for Teachers and -llchnicians

(,p€a.50n Education Lim.ired 2009

pages 66-671 a 'lhc hcat of the body is producerl as a resuh oi the mctabolic reactions taking place,parricularly respiradon in active tissucs such as Lhc muscles and rhe brain.After death

thesc rcactions slow down antl str

rime he a t energy is i o. t uy,o ai"ulp,., ;:"::;:::*:';::l? ::ff :1111;ll ?J,i $.evaporadon so &e body cools down.

b rhemctabolicreactionsdonotailstopimmcdiatclyaftcrdeath-manycellsconrinueto respirc, conuact' rnd so on, unrir arl rhe availabjc oxygcn and ATp is used up. soheat continues to bc gcncrarcd in the first hours aftcr j.",t-r,

"trr,ougl-, at a slo*,er rare,

so body tcmpcrarure drcips but rclarively slowly.c 'lhc tcmpcralurc glallie rll bclrvccn rhc boely and lhc cnvironmenl wili affect ratc ofcooling, for exalnplc if somconc dics insidc a warm housc the body rvill cool down

more siowly than ilit is on a cold rvindy hilisidc, so rhe cxternal temperarure and.wea*ter condirions have to be takcn into considerarion. A naked body rvill cool muchfastcr by convection than a ciothed body, and a body *,rapped in blankets or a duvetwill cool down cvcn morc slorvly due to insulatron..t.u"ttody will cool laster thana dry body as a rcsult of l.rcat lost as drc rvatir cvaporxrcs, and dearh in a warm bathor

leside some lorm oiheating will also change rhe raie of cooling. Even the body

posirion ar{ects rhc rltc of cooling - a srretchccr our body has a much bigger exposedsurlacc arca 10 volulne ratjo fiao a curlcd up onc ar.id so wrjl cool dorvn faster. All ofthcsc diflcrcnt factors huvc to bc takc' ir-rto considcr:rLion rvhcn using tcmperarurc as aguidc to tirc tintc rrf dcarlr.

2 vcry littlc differcncc as rhcy arc poikilothermic and so their body temperature is normallyvcry similar to rhe ambrent tcmperarure.

3 Llmitcd valuc bccause, although thcre is a gcncra)iscd parrern ofrigor, there are large'ariarions rrom one individual to anothcr dcpcndi'g on factors such as:' amount of ATP storcd i;.1 tic muscles ar rhc rirnc of'dcarl.r which depcnds genctic

tendency and lcvcis of fttncss

' Icvcr oI acrivity bcrorc dcirrh - rr'rv nruch dr-r) hus bcc' uscd. tempcrarure oi the individual ar frc point oi deadr. teinpcraturc of rhe surroundings

' spccd ar rvhich rigor passcs ulso cjcpcnds o' J vf,ricty of frcrors sucjr as cxr.crnaltcmpcrarurcJ acdvity of cnzymcs.

Other examples may be valid.

pages 68_71

t ll:,lt:"

srallc is causcd by r'hc coroniscrs - rnacrobic bacLcria. EqTymes rrom lysosomcsorcak down cells releastug cell conrcnts on rvhich anacrobic bacteria grow. As more cellsare broken dorvn, the bactcria sprcad.

' The bactcria are rollorvcd by a numbcr of species of flies, c.g. browflies, rvhich layeggs'The larvac (maggots) leed on the rissucs, bre aking their down further.. As rhe body liqucfics, adulr ilics can lccd on ir too.

' Bccdcs arrivc whosc iarvac lccd on maggots. Parasitic rvasps lay their eggs in thc larvae.Ede\ccl A2 tsiology lrnplementarion anrl Asscssincnr Guidc for'rcJchers !ndrcchnici:ns opcarson E(ru*iion Lrrnircd 2o09

. When *;"""'move in. ""* s'rqrsn[ spccics such'as t.l-,e Ehcete fiies

,n".,", *,,i'li]::"f *. body arc roo

h i, r" r,..,r.i.t' *one .h.,uin

J ; Jj ;::XT:l: T::: ll_,,.*: any more, bcede

, ;r"^jr::,;:;::::: morh iarvae reed

. -.b ldrrass bcedes, ham beetres and

notj'ihsr'de

".;f,l:::.:'ll:'"' "'. ,",;o:.; on the hair unril onlv drv bones arelert.

''ct"a,. ."icntn,lutside)' bui t"t

"*"t t'iio'turc tnd JcvcJ

'r cxpusur"'r

r cnr pera ure .iil,f T:::*, sh ourd bc r,". ]'-':','"u'o';;;; 1l, "i n:ilH:i:;rarc and,"*". llll

t'he ratc of clrcmt*,l."lt of rl-re cllect on dccn-^-^: '

avairabiriry "r rllTililll'l ;*,.l#::]'vmic rcrcLicns -

"'*;'t"j:"n' For exampre'

3 succession foir, Y to insccc t;t"-^,:,:. tl.re lcvel

"tt-ttrr.. ,fri,i;?::ff;tt"t,long *in'o]..jotvs-a

regular patrern sor bv e.ort'irol'rruion th" condiio,,;;;;:?;.':'*ining fie srs.c ors,,"^- ..

ts+cJ 4 a Exposcd ooo

n"'"'t'.*,. "ri",",jl'"[,t^""t1]:1:,0"'" ^;r,;,;;.:ff:on

in a bodv'

;:TffTffi il:li:ii: 1,1" H'ruiii::: :;x ;:;-.r c s c cn s s ca n

;:'.'";ffi::l;r:^tdm,*i{[$:":,1""i',#l',n:J;:::"?.t:.h"ng"", ,, ., ,I_tl-oeraturc shorvs less ra c ri vi r y or th c

jll'j:'1,'. il;;::;iff::: :: ":, " r; ;;: ;'r[. "..

b AdvangSgg5,'' lssomposing

organisms. -" '-rirpcraturc are duc ro variadons in the

wrth obtaining '' fcwcr cr'hical issucs' '"'" ^

Disadvanl2ggs. l::::'.,'';;":;ll ;:].,j,:u"' orpis carcasses, rewer probrems

organisms, a;rr.flgt arc not pcople, so r,hcrc

ff 'ffi

iltit:f;:t'-$;',;.:;:li:.:[::'i;']Ji"t""it'_1,ii."",,,"c Advantages:

Lhe rDiscdvanragcs:

",:::]:: "' d jrccdv

rcrcvanr ro

nurnan bodics,,,;li:1^,::::'"lJ*r,-.,iri.:.. ,::::'tisation of hurnan bodies

A ny o rher,.,. ;r;; ;:;, r

n cre h um 3 n rc m e i n s ;;";: ffi l'ffi :XT.H: :ri:l:,',pages 72*77

il;* =:r1;av,

it drres ",""o *ffi;;;

I rr ^^--::.,:,,,1r, rnore informar.

;Ji ::: i:: _TH#:;T TiH[:1 fi 3j x:* n r s,,w. or,h e *u eei:;:{''i",".. i:*;J}iil:":x,ffi I*"^f :T,Hlt,fr

r..,,.,,o::::'" 't "..i'"-""'il,.j ;:'^:::T'*"" *r* *i""L" l^i"

*: or rhe three

H' i,:ffi i;t " t**i :id;l : ::l it ; H ":j::il : ::1,r,: ff ::,;T: .*.I?J. i,:ffii;1":,Y::-: $ffi:::::l;H"n;;:^"

1"'"''" '1's is imp'r'[an'l

il: ;;::il"I.,].ll ii,i ; :::unna n, rc rc', c, n, cd''

Jff;;:.*.; :: ;ffi::;t; *m#:friifr ilr i;:I T: J':..l.ffi i,"..,..m

="

. ff*iJ":,?#;:*ff i'i,rffi Ili,lliHli-..,.,..il::iiiffi.:,":,?il:,,.";;;;il:'";ilil:iil*.:j;:.J*j::i',,T;l;;,: j:;

,u acld ln a specific place in an

am.ino ac.id cha.in.

Edexcel A2 Biology ImpJcmcnradon and Assessmcnt

Guidc forTcrcllcrs andTccl

-

uicianscPors"n' -

2 [s+cl -fhe ansrvers should includc some oI all of the following. other points may be valid'

.iianscriprion:ArcgionofDNAunravcls.onlyrhc5'primeDNAsuand(thetemplate

or anlisense suand) is uanicribcd to give a singlc suand oi rnl{NA''l'he uanscription is

broughtaboutbyanenzymecalledDNA-directedRNApolymerase(RNApolymerase).Evcry rr.iplcr

"oJ" on the DNA givcs risc to a complcmcntary codon (uiplet of bases) on

tire mRNA. Every rhyminc in tl-re DNA rempiate is replaced rvith uracil in RNA' Apart

fromthischange,tlrenewlySynlhesisedl{NAsuandhasthesamesequenceasthenon-template, coding or sensc slrand of the DNA'

Translation: mRNA molccules pass thIough the pores in the nuclear membrane and

movetothesurfaceofrheribosomes,transporlingtheinstructionsfromthegenestothesirco[proteinsynthesis.Eachtl{NAmoleculehasaunitofdrreebasesaroneendofthemolecuiek,'o'"n",thcanticodon.EachIRNAmolcculcalsobindstoaspecilicaminoacid cJcpcnding on thc cotlc of thc anticodon'.fhcribosonrcsarctlaclculrol.alargcatlr]astlrrllsuburrir.-llreyarc5O%llNA.Thcy

surroundthosepartsoithemRNArvhic}-risbeingaclivc}yfanslated,andthenmovealongrodrcncxrbit..fircirjobistoholdtogcthcrrhcnrllNA,IRNAandcnzymescontrolling thc proccss of prorein synthesis in tl-'c corrcct posiuons'

ThcribosomcstartsrcaelingtlrenrRNAataSl'artcodon(AUG).Thiscodesforlheamino acid methioninc. Molecu'ics of transfcr RNA carry individual amino acids to the

surface of lhe ribosome. Each tl{NA lines up its anticodon alongside a complementary

codoninrhemRNAandisboundinplacetotheribosonerr,hileenzymeslurkrheaminoacidtothcprcviousoncitrtl.tcaminoacic-ieiluirrbypcpuclcbonrjs.oncciisjobisdonc,theIRNAreturnstothecl'roplasrntopickupanotheraminoacid.Theribosornemovesalongt}rcmolccu.leolml{NArcvcalingonccodonafteranothcrunulthcendisreachedat a slop codon (UA.A^, UAC or UGA)' producing a complered polypeptide chain'

.3 ts+c] Theansrvcrssho\rldinciudesomeorallof thefollowing.ot]rerpoinrsmaybevalid'

TheyusedthemouldNeurosporacrassawhichhasashorrlifccycle,iseasilygrownandmurarcs easily.-I1e original srrain of rhc mouid could grow on minimal medium (with few

nuuicnrs) as it could synthcsise all amino acids and sugars it ncctled. Moulds were exposed

toXraystocauscmutadon.N4utadonsinthcchcmicalpathlvaystharaffectedtheability

to synrhcsisc particular amino acids would show up casrly bccause mutated slrains needed

one or more nuuients added to the growth medium othenvise they rvould die. Crosses of

differenr sfains rvere carried out, to show drat dre ability to synthesise all amino acids cou]d

return and be passed on. From thc evidcncc of many experiments came the hypothesis that

a single missing cnzymc was rhc rcsuit of tl-ic mutadon of one gene'

4 Scicnrisrs recognised that rhc cnd result of a gene was not always an enzyrne) for example

that it could be a structural prorcin or some othcr rypc of protcin and so the definition

became broader, As rhe suucture of complcx proteins like hacmoglobin wele unraveued)

scienrisrs rcaliscd thar sc.rmc prorcins wcre made up ol scvcral po$pepride stlands).and

thlt ciilicrcnt rnrriarions changcrl diffcrcrrt polypcptidc strands which shcwed the gcncs

rvcrc cociing ibr indivrdual polypepticlcs, not ahvays thc samc thing as the final protcin'

5 .iye now know rhat diffcrcnt proteins can bc manufacrurcd from the same gene, from *te

evidcnce that.all r|rosc protcins arc alTcctcd by murarion in tl.rat gcne.We also understand

thar pos!-ranscripdonal changes may occur in mRNA, lrom observations of the action of

spliceosomcs. OtJrcr poinis may bc valid'

lldexccl A? Biokrgy Implcmcnration and Assssmcnr Guidc forTeachcrs andTcchnjcians oPexrsoo Educatjon Limiled 2009

irli:rji!;

::rt.lt,Pages 78_81

I * is the producrion of an anarysis of rhe DNA of an individual based on mini- ormicrosatetite groupings from a limired ""*b;;;;;;"ns which can be compared withsimilar profiles from ou\er individuals.

2 Used to produce a DNA profilc.. 'lhe srands of DNA I

cndonucleases *t i.h ,.o* a sample are chopped into liagmenrs using resrriction

Dirrerent resrricr"" .il:::iliffi :::Hl J,",ff ,l,fi :::T ;::,*T:.sequences knorvn as recognition sitcs rvhich are found ar cirrrer side of mini andmicro-satellite rrnits. leaving repeatr:d ."r.,,r.,,..r',n,r.r.. The fragments of diffe

f ragmcnts"..pr,..ai.'TJ,I:T1T".J,:.;:::oJo:if i:T;:i,:ff _Tl::J.:mainrain a consrant pH).

' The ger contains a dyc rvhich bincrs to rhc DNA fragmcnrs..I.hc dyc wilr fluorescewhen p)ace d under LJV light, rv'ich _rt", ,1."'ON^ bands visible rvhen rheelectrophoresis is complete. Ti" n-lor, .o*rno,r,r'ur.O ay. is EtBr (ethidium' bromide). A different dye is also .aa.a ," ,fr. ONathe sample s .. uh.y -ou. *uough thc gel.

' samplcs to shorv the posirion of

*"::""i:"J:;:JJ::"',:"9 through the appararus and rhc nNA fragmenrs move

rherragmenrs_"".;.,"i;i.0.:.;X."J"ffiH:':;::f ;,n**l?:,i*:XDNA fragmenrs are usually placed in a .;r;;i;; .. When elecrophoresis is complete, the plate is placed under UV lighr. The DNAfragments fluoresce and shorv up .i.u.ly," il;;; be identificd.

I'his is the original mcthod:f p"" fingerprinting, rvhich needs a relarively large sampleof DNA ITslrowsuplargcDNarrrgmJnrs.r",rt,"r,mjninrunrol50basepairs,i.e.minisatetites However smalrer regions

"f DNA i;i;:sutcrJitcs) and specific genes canno\v be idcndficd using cxtcnsions o[ this t".t_ln;qu".

a The porymcrase chain reaction rcpcats dre normar rcp)ication orDNA using theenz),me DNA polymerase. The reacranrs _ ,fr" OI,IApolymerase, primers lsmatt sequences of DNA ,,uhi., t"-0," to be amplified, DNA

th' ,"p"."t.i DNA ,;; ;J::":::::-:1\^ lvhr:h. mu:t join to thc beginning or

n u cl e o d d e b a s e s _ a r e {::J:jn:",: f :'r: I Tf,' :l ;;ffi :,e:*;,;h:The reacdon mixrure is first heatcd ,o so-g5t i*.00r,30 seconds which causesthe DNA suands ro scparare as rJ-e hyilrogcn bonds hoiding drcm togerher breakdown. The mixture is then coo.led do*n to 55_60 "Canneal) to rhe singre DNA suands. r.rnuuv rh. ilJH"T:::T:.r,"li:11."..,ar leasr a minute,This is thc optimum ,.;;;;;;

w_hich builds ro .o,norn..n,a ry s rands or D NA I o"; :: : X ::'#..,.fr :,:IiJ.'llhese three basic steps are re rcated around 30 rimesof rhe original DNA, druuro JU trmes to giit :round 1 billion copies

Edexcel A2 Biology lmplementation and Assessmenr Guidc for'ftachcrs and rcchnicians opea.son Educadon Limired 2009

4 a Traces of biological matcrial are uscd as a source of DNA rvhich is amplified using

pcR and then used ro produce a profile. Because the chances of wo individuals

having the same DNA profile are extremely low, when the DNA proflle of a

suspect matchcs DNA tiom thc crime scene rhis is takcn as sfong evidence of rheir

involvcmcnt in somc rvaY'

boniyidcnricallwinslrrr,cjdcnricalDNAprofilcs,lrcrlvcvcrfamilymemberdshorvmany morc similaritics than non-rclated people"so, if rhe DNA of a suspect of one

ctime is checked, if DNA from anothcr family mcmber is on the database, it will come

up as a close march. This can lcad policc to thc rigirt suspect) eve n if rheir DNA is not

on drc databasc.

rcel 42 Biotog) Implement.don and Assessmenr Guide for'lcrchers anC'ltchlicians gPcarson Educatioo Liniled 2009

Pages 8z_832..\

X UJ ' Extemely small so can casily ger jnro rhe body.+ Sirnple s,'ucrurc of prorcin coar and gcnetic matcrial mcans rhe virus can wilhstandharsh condidons and rerain infecriviti

::i:."tr"r a.achnrcnr poinrs (VAps) ro cnablc thc'irus ro :rrr:rcir ro spccific tvpes of

. Some have specific mechanisms lor injecdng rheir DNA inro cclls.' Virar geneLic matcriar is adaprcd ro take over hosr cclr -..n"r;r;;. For example,

:::::Ti:::, direcdy as a temprare for borh neiv viral oNa ,.a i,,rre mRNAs

rranscrip rase #.il::::J,:'3"i:K:' "irr I RNA u""' o'i,",r.*",', or rcvcrsc

is then used ,, ;;:;:::: :'^::i","^^ corrcsponding to the viral genome which

gcnomc. a template lor new viral proterns and ultimately a nerv viral RNA

Orher points may be valid.

ts p tS+C1 'l}e answers should include somc or ivalid. irrsluse somc or all of the ibllowing. Other poinrs mav be

a Like living organisms, they reproduce, conobligate lnr...uurr. orrrlr"""r'""l"ll;.illtarn

genetic material' undergo evolurion, areother living ";l:n:;*"'es

(can onlv exist and reproduce .r'o^..rti, in rhe celis oftr Unlike living organisms, drey don,c fecd, respire, excritc, movc, or shorv anysensidvity The onJy characterisdc ofriving *rings shorvn is reproducdon.

pages B4_85

L! tS+C1 The ansrvers should include some or a.. valid. ,rLrucre some or ail of the foilowing. Other points may be

Lyric:virll gcne.c mrtcriar is rcplicarcd indcpcndcntly of r_hc host DNA straight afrerglterir.rg th,e host celr. Marure ri^r.. u.. -i'. uy host ccll, which evcnruauy biiris anareleases rarge numb.rs ofnew virus ou.,i.i.r.rnar. go on to invadc other hosr ceus.Thevirus is said to be virulent Cir.r,._.;;;;;;. 'Lysogenic: Viruses

r

DNA inro ,n. h.,;i;lT:;:::'::;;::L':::.:':t gcr inro rhc rr.sr cc' 1hcy inscrr theiris produced t o- th"

"i.-l DN; b;:";.". .7.3: *,t hosr ccll divides.No

'RNAof a repressor prorein which -"u;ii;|;rr;o:::"-u''"',4'n"s causcs thc producrion

ffi ::t""3;::::,1:*"'"'ao'-,o".vi'I,,"'il:il::il.lilx'*il:t;::'"'r^ Jiuons'

'l*]j a Reroviruses have RNA as genedc mareriar iniread of DNA.b They have more comnlpw tir^^..^r^-by reverse

",,.J;;::T'["j:fi:L::RNA nrst has to bc rransrared inro DNA

il:Ht,*:::erted into ,r,. r,,., o*a. v,;li 3",ifi:'#:?:l:.,i:::: ,:,i1"

proreins ^"0 "*.i, .ilff ll,T ii}iliiivira

I m^NA a c Lr;' ;,"*;:: l*,'"*,,i,"r

Edexcer 42 Biorog-y Impremcnrarion and Assessmcnt cuide fofTcrchers and rcchnicians opcorson Educstion Limircd 200g

d!,'rnx!,nF{i$rr7f+f,.ttF!{@rtsjftlqiir:i:J@&ratrs,$t!LrKd6lfd&-8rs&1x\*F!}*F$r:!:titjwRl:rani*{}'Jst'It

:'::il,tiirr'rii..,Jii;il'';llfj

pages 86-87

,i"r

tf 'r

pages BB-89

li) a Rapid, reiiable - can occur cvery 20 minutcs in idcrl condidons

. b Brings ab<;ur gcnctic variation rvhich can cnablc bactcria to survive unfavourable

conditions.

(2'; z h shows that genclic material can be taken up by bactcria in sflficient quantity to\-/

bring about a changc in chrracrcr of the organism. and in this casc make it infecrivc.

b Whcn rhc dead bactcri'a wcrc attackcd by cnzymcs t]-lat dcsrroyed cerbohyd-ratcs

and proteins it had no clfect on t]re ability ofthc transforming factor to changc

the R bacteria into S bactcria.This shows t-hat the uansforming factor is neither

carbohydrate nor prol.ein. However, rvhen the DNA is destroyed, the uanslormadon

does nol rake placc, providing strong evidencc for DNA as the transforming factor.

vX^ / R iS+Cl Thc ansu'ers shouhi includc sonre or all of thc following. Other compararive' \)-- points may bc vaiid.

5tructurai features Animal cells Bacteria lMruses

Average size (mm) '10-i00 0.5-10 0.02-0-3

Cenetic materiat DNA DNA DNA or RNA

Outer tayers lipoprotein cell surf ace

membrane

cel[ surface membraneand bacteriat cell

wall made of

peptidoglycan witholher compounds

such as teichoic acid,

lr po polysaccha ri d es

may have slimecapsule or lrytr

may have an outerlipid enveioPe

protein coat ot caPsid

made up of rePeating

ca psome re5

Main inclusions nucleus conta'nirB I cytoplasm

generic n ater.al I geret;c ma:e:'al

(DNA) | {or'r.n)

ribosomes l'PLasnidsmitochond.ia l'mesosomesColgr body

I

tysosomes I

vesicles I

cytoplasm I

cenrriotes I

c)'tosLeleton I

vacuoles I

endoplasnric I

reticulum (RER and IsER) I

genetic material

Movement varie5 - may not

move, may be

amoeboid, may use

cilia, fiaBelia, etc.

may have i,agellae I

. :il'.

movement

Edexcel A, ;riology lmplementarion md Assessmcnt i lrlc for'lcachcrs and'l'cchnicians Ol)carsur l:ducaLion Limited 2009

*{ses 90-91 -**''"*w>Ejoeicirii*;[;i;aiH

1L/ts+c] Thc answers qhn,rr.r i-^r..:

* Ill":,, .,,,. o,,.j,lni).|ff::::"tr;:,]:'|."'forlowing other points mav be varid' nelv viruses.The host ceil" ..a,,^!_^,1 , olism of the cell and causing it rn *-r.^

F J;:;:'fi I lil.T'i:::' ;"" il:;":ffi ;i IT: ::: .ffJ5i: ji I1-',Tm I ;r,,,: 3li;,

=;ff

; T: *: :: : il;lil ; ;: m ;*".r*;l ;: fi ::::,Bactcria: Cause diseasc rhrn,,-h ,u^ -nndc,rox,ns

".. ,,ooo","r*il::f: #::l;l::u.,,, rhey grou, and reproduce.I hev ofien cause fevcr, ut"..n..ll,,l .;:"t :::* laycr of Gram-n.guriu. u.",.riu.

il::::'fili:i:,,"Jj:ff "T::';;;;;,;;:;;.l'lTfi ,::;::,iili:'i:llr:::c o,

i:.,- ;;;.:";H,:ff .:., ;I * *' o''"'*' *;::::iT;::?:,.,

- carbon compoundsor water.

in decomposers, carbon .o;uuotuttt stages: dead orgaoic matter

rpounds in decomposers + CO2 in airpages 92_95

$ ts*c] The ans,,vcrsvarid. Sujrabic .rbr" ,,:::r11

incrudc sornc or uil c

' vecrors:,."rn.*j, ii"li*,:.";;;l ':; ::t''" ftrrrorving' otr:cr points mav bc

. fomires: narural skin ffora and sebum. direct contact: skin. inhaladon: -"",; ;;:;;.:,Til",#,,tt"ingesdon: saliva, mucus, stomach acid. inoculadon: clotring

'$ Lrrorr*.s are enzymes rhlr .,. ,_.r^",-^_. r

mucus rhat line' ott ..'111t-tan clesrroy bactcrial

<

acr to desLroy bn.,".ir, ]:i'j:o" """-' 'n" *;";,';;"t' rvalls L)'sozvmcs are prescnt in the

are also present,r.r,.r.,"o,"1" patricularly tilil:

ur:nary and reproduclivc tracts'They

.:-\ and dcstov il;';;, .:.'gt'tlt Gram-positive bacteria.They

lj) Phvrl.rl barriers: ural cnler and might infect the eyes.

. Skin is a tough watetparhogcns ,."", ,.,",llollcuter

layer impregnared wirh kerarin rhat preventsceris and

"",u;;:;*',:*;::?j:j::""t, brood-rich rjssrrcs rvrrcre ,r,{,

"oura i,,u,a.. Mucus forms a sLiclc

,, o.n, o,*".";,;::,:1:: *n'ch acrs as a physic

. resp ira ror v,,,., " "

o lTiJ"''''; ; ;",."n'# il'J J:lTl : : "ff :;TfJ

ilr ogen s

Chem.ical barriers:. Sebum is a laycr oioi

grorvth of pathor.ni.'ot top of the skin that con:

skin b a cteri a. _o_. _, 1,,. t..i, b", ;;; il; "",1,;:' ::il Tj.ilT..:,,ffi ,X:;. Acid in rhe stomach h

desrroyed

', *", ,.";T.1T

pH and acts as a barrier ro mosr pathogens rvhich areEdexcel 42 Biology Implementation and Assessmenl Cuidc forTLachers and Technjcians ,Opcarson Educatjon Limired 2009

iii::::'til

''i::'._..J.::i -itt:i: i:

l1:iiiiiiii'in:S.1t3.*;r!rr:':'

Biological barriers:. Skin and gut flora - thcse arc tire hcalrhy bactcria grorving on the surface and lining

thetubesolrl-rebody.'I.hcyoutcompetcpathogcnsandprcventthemgainingcntlytorhe body.

Lysozymcsarecnzymcsfoundinn'rucusatrdrearsthatbreakdownbacrerialcellwallsand kill ihcm bcforc thcy can infect the tissues'

ThevomitingreflexejectsbactcriaandvirusesfromthebodybeforeaninfectioncansPread far.

AnY other valid Points'

oaPes 96-99

o Masr ceus and damagcd whltc biood ceils rclease chemicals known as hisramines

:'rvlriclrcuusct]lcblorlJr'csselsitttiteutelt,llrrtieulrril,())eilltcriulcs,ttlclilutccrusirrgs4'\wlocalheatandledncss.Hcatreducestheefficicncyofreproductionofpathogens.

. Histamines aiso makc *rc rvalls of rhc capiilaries lcak-v so fluid, incluciing plasma, white

biootl cels and anribodies ars forced our of rhc capillarics causing swelling (oedema)

and often Pain.

..$Thiteb}oodce.Ilscngulfpa*rogcnsbyphagocyrosis,anlibodicsinactivatepathogens,

pain makes you takc care of iniured sirc'

2l]ccauscthcysimplyrcacttonol]-Sclf-tilcrcsporrscisnotspccifictoaparticularpat)rogcn.

3 a A raiscd lcmpcraturc can hclp rhc body combat infection by lowering the

'-^""1"'1ion ratc of rhc pathogcus' Also thc imtrunc systcm works bcttcr at highcrrLPr uuuLuvrr

temperalures and so rvili be more succcssful at combaring thc infection'

blfbodytemperarurerisesabove4O.C,thedcnarurationoisomeenzymesmayocculcauslngp.,*un".,,tissuedamage.Ifrlreremperatureisnotloweredfairlyquicklydeath maY result'

Edcrcel A? Biology lmplemcnl,lion md Ass6smenr Guidc tor Tcichcrs an'l Tcchnicians OPc'rson Educa!on Limtr'd 2o09

pages 100*.103

Q rrr" imrnunc sysrem re

:l *: o"o, n*. ."ir;:: T:: ;.T#"#il:: i' surracc or p arhosens. rhe ceus

anack thcm. -'! urrlrrurrs system recognises as selfand so does not

@ B cells:These have receinvading t;;;.;r:ilttor

proteins which recognise the anrigens on rhe surface r.rfpathogen. - '-eY Sive rise to cloncs of cclrs .halrilriuc9 a'ribodies to u ,p".in"T cells:These come in tproduction of anribodie

types 'f helper celis produce chcmicals that stimuiare ther\ s. T killcr cells produce chen(+) Non-sp.crnc responses rccognise ,n. ;".J;." ;";:''^t'

*:tdcstrov parhogens.

gcncral reacdons against anything thar is non-se'. o.ll"n ttttont' non-sclfand iniriate

response invoiving rhe masr ceils and ,h. hir,r;;;;:1:;j:: :l.?;,::1,-_".,The specific responscs oVe ry specific andgens

""lt:-1--'""^system rccognisc nor just non-scll but also

p a,h o g c n s,,'. o ;". ;;,; " ;,: i *fi

"': fi : il;T # TJJ t* *Tji1*.11:.,,..

Edexcel ,A-2 Biology Implemenration and Assessmenr Guidc for Tlrchers rnd Tec)nicians 6person pducarion Umited 2oos

fages 104-105

C ' Disinfectants kiil bacteria lrom the area, lrom insrruments etc.This ieducei the*:- Iikelihood of bacteria bcing uansfcrrccl from cnvironrnenr to the patient/wound.

' Antiseptics are applied to skin and to wounds.They kill bacteria and so reduce rhelikelihood of wounds becoming infecte d, bacteria getting inro blood etc.

' Anribiotics desroy bactcria rvithin a parienl and so rcducc rhe likelihood olinfecrionpassing from one person to anodrer through cither dircct or indirect contacr.

@ a lndrcl80Os'3{J0rvot.ttcnrlicclperl0OOOObabicsborn(600-900womeninfectcdpcr

o 100 000 babics born). lh thc carly 20OOs cicar-hs terc 0.85 \romen pcr l0O 000 babies- DOrn

G fft"i. work was important bccause it shorvcd clcar cvidence for rhe eflectivencss of\-/antibiotic drugs in trcating a bacterial infection which killed many young women eachyear.

It feU short of modcrn erhics and standards because rhcrc rvere no lab trials on dssues

and cells, no conuol patients rvho did not receivc the drug or who received a placebo,no doublc-blind trinl, probably no plticnt pcrmission for rhc trcatmcnt sought, and noethics committee decision on rvhether thc uial should go ahead. Other points may bevalid.

pages 106-107

(! fi." following describcs the basic inlormarion. Orher dcrails may be found from research.\r' Ronald Hare, one of Fleming's young assistants, found that penicillin mould grows

best at quite iow temperatures.

' Dr Cecil Paine, ano*rcr onc of Alcxander Fleming's pupils, was rhe fust person totry peniciilin our on peoplc. A local nriner got a stone in his eye and had a massiveinfection rvhich was making him blind. Painc washcd rhc eye with his penicillincxullct, and thc cyc rccovcrcd. Painc also usccl his pcnicrllin wash to trcxt a tiny babywhich had pickcd up an c1'c infecdon as it was born.The baby was curcd and irs sightwas saved' Painc nevcr publishcd what hc had donc, bur he taLked to Howard Florey, anew professor at the uruversiry, who wcnt on to follow up the work.

' Norman Hcatlcy rvas a kcy man in drc Oxford team. Hc worked out a way of makingenough pcnicillin to text it and carricd oul thc following cxpcrimcnr. Eight mice rvereinfected with bacteria which would kill them in 24 hours. Four were given penicillin.The four treated mice stayed hcalthy - but rhe orhcr four died. In 1940-41 Heatleydcvclopcd special pot vcsscis so hc coulcl grow morc mould and so collect morepcnicillin. In just a fcrv wccks hc had madc cnough pcnicillin for Florcy to uy ir out on

. a lully grorvn man.

' Mary I-lunt brought a mouldy mclon into t}rc jab tirat shc had found on a market stall.The mould was a new sort of PerLtcillilnz which produced much more penicillin than*re originai srain.Thc ncrv mould rvould also grow in big fermentation tanks ivhichwas the break*rrough which cnablcd industrial producdon to go ahead. Ms Hunt gotrhc nickname'Mouldy Mary'.

lldcxccl A-2 B . 'rsy lmplemenlalion ud Asscssmcnt Gu: I iorTcacl)crs andTcchnicians opcarson r :rucrtion Limited 2009

l^t2/ u Ant rrvo examples of rhe aclion of bacter ia clearly explaincd.

means it kills bacteria. Bactcriosradc means ir stops bacteria grorving/

b Bacteriocidalreproducing,

" ,arH::lTi::i_ some andbiorics are bacteriosraric.ar.rerari'e)y

low concenradons,infecdons,

" G.; ;x:::;Tffj::::1J,": rlrc inlccrion,;;;,";; ;;;","""."pages 108_1 1 1

1 Mutation causes a change that arfects the way the antibiotic gers into or affects the bacreria.The antibiotic is a selecdon facror by Liirirg.u u*.lia thar arc sensidvc ro it.Thererorerhere is rapici evolution so that rhe rcsist*, orn. i..""r"s lre mosr .orr*o,, iorrr,.t " f,l:, The answer should include some or ali of tire following. Orher points mav be

Keep antibiotic prescripdon to a minimuml ensurof treatmcnt with anubiotics; be espccially careful fJlat padcnts complete the course

anribiorics in *re case of C. dilficite. with the use of broad-specrum

b Minimise exposure to reduce rhe lik€lihood of rcs.Make sure that rhe whorc course or.anribio,,., ,, .r,rur, mutation being selected for.

srighrly increased resistance are definiteiy

"u.o ".:::;l;;racrcria rvith onry a

3 a Broad-specuum andbiolics wipe out large numbers of the normal gut flora so c.dfficib can get established, produce ,"*ii; ;;;:;. b Narrow-specrum andbiotics are urscred

", *".:^:::::,:Ttt"*''spccific infcction. so they arc lcss lik"cly ; ,;;;;:l-tms rvhich are causing a

minimise opporruniries for c. dfficite;" il";.::,ff,lt.::: r,,tora ancr so

4 }ixamplcs of good practicc inclrrcic:. Docrors, nurses and. other health carc prolcssionalrarcc':hoi based gers between seeing parients ,..""J;;t[* jTiil:';'.",':"treciuccs chances of passing ti.,..n *. So";*-;;;;arcohor gers ,o ,h.rJ;. orrimited u,. i. o",i,"iil,*Tff;:h,"1"J,": ,r

"". Avoid clothing which might carry bacrer.ia from pat .

rvarches and rong_srceved shirLs ir-he.,* .;;'";:;r.;;:::,ll:.',,e,g. rong rjes, wrisc

HeaJrh professionals wlrom the outside.

,ear steriliscd scrubs ail drc time to avoid bringin$in pathogens

' Monitoring parienrs lor inlecrin^ r_t-- -r_:-_.avoids spread

"ro.*.;j:l:t'ion rvhen admitdng and rreaung and nursing in isoladon

' Encourage visitors ro uinlection into hospital i:':ffiT il:

use alcohol gels to minimise risk of bringing

' 'fhorough cicaning oi hospirai.war<isr roilcis, bcd pans ctc, prcvcnrs and conr:ols thespread of disease 'i,v removing br.r..i., fr..;i;: :-, ",".. Using chlorine_bascci disinlecrant to be sure C. dirlic;lcis destroyed.Any otlrer valid points.

ljdcrccl n 2 Djolo!,y lmplcmcntario I 3nd Asscssnrcrl 6uidc for-ltrchcrs !nil.Ji.clttic;rD3 cl,(,!rsoo Educarjon Limilad 2oo9

Pages 112-115

1 Natural activc immunity: Inlcctcd by pathogcn rvhich mry rcproducc and cause'sylnptol)ls of discasc.'l-lic inltlurtc sysLcm is lctivatcd unrl thc imnunc.cascadc iniriatctj:B cells, antibodies andr cclls produccd rvhich dcsuoy parhogcn. Immunological memoryet-rsurcs that if the pathogen is mct again, *rc immune systcrn is acdvated before diseaseresults.

Natural passivc immunity: Anribodies against various diseases are passed from mother tobaby through placenta or in brcast milk- Short-tcrm protcction against these diseases as

immunity is losr widr time,

Artificial passive immunity: Antibodics produccd in onc individual or animal are given toanothcr individual if drcy havc comc into .onto.r ,ultl, a panicularly dangerous or rapidlyacting pathogen, e.g. letanus. Short-tcrm protection as no immunological memoryinvolved.

Arrilicial activ€ irnmunity:'ll.rc immunc sysrcm is cxposcd ro rlrc attenuated pathogen(e.g, dead, inacrivared toxin, attenuated livc organisrn, protcin coat fragment or DNAfragmenr).This srimulates rhc immune rcsponse.The immunological memory ensures

that if thc live pathogen is encounrcrcd again, B ccils,T cells and antibodies rvill dealwith it bcforc it can causc symproms of discase. For cxamplc, vaccination against polio,rvhooping cough ctc.

2 Astlreantigenporrionofvaccincbccomcsincrcasingiypurc(bitsofproteincoat,DNAfragmcnts ctc.) somct-hing clsc is nccdcd to srimLrlalc inflammation and thc full,blorvn

. immune response.This is thc rolc of adjuvants - researcfi into best material to use. Anvother valid points.

3 a 'l'l.rcy arc l)ot inlrnunc [u drrr diseesc, thcrclbrc if thc5, nrecL drc padrogen in ariscounuy or abroird rhcy are likcly ro become iil and may be permanently damaged ordie.

b Ila child is not vaccinared, ir may carry infcction or become ill and put otherunvaccinated children (e.g. those allergic to eggs or rvith compromised immunesystcms) at risk of the discasc.

c' From anindividual point ofvierv,completely ethical. In lactircouidbercgarded asuncfLical if parents did not have a choice o';cr rhcir children,s treatrnent.

' From a socictal point of view, it could bc argued that it is unethical rhatindividualstluough ignorarlci, misconccptions, laziness or indiffcrence could compromise nottlnly rJrc healdl of tllcir orvu cirildrcn irut also thc hcalrh of socicty as a wholc undthe rveakest membcrs or it by tlucate ning rhe cirnccpr of herd immunity. So fromihis perspecdve it is unctrricar that parents can deny rieir child immunisation.Any orher valid poinLs.

I-'i r\ccl A2 IJiolon' lnrplcmenlrtion rnd Ais,: , r n cnr Gui<]c Ior -lcrchcre

and ltchnic[ n. ,! I carson .Lducrrion Limi rcd zoog

4 A link benveen the whooping cough vaccine and brain damage rvas suggested,Therncdia took hord of tlrc story irrLl publis'cd ir, rrut ig.orcd drc rnct rrrat whoopingcough is known to cause brain dam"ge in some chiidren rvith a quandfied risk. parenrspanicked when they heard the-srory and didn't rake thcir ch'dren for vaccinadon wirhthe rvhooping cough raccin". More childrcn *rr.t"d ,uff".ing from whooping cough andcases bfdamage caused by the disease began to be seen again.The scare was shown to beno more than a correladon which had caught the eye ofa doctor rvho became convincedof the problem, in spite of a' evidence ,o ,h" "onou.y.

It took ycars for public confidencein the vaccine to be restored, / !q' ! rvr vuu'e uur

Materiar on MMR as produced by students.This shourd covcr hor,r,concerns over theNIMR vaccine came about; rhe efrecr of rhe media and how the story rvas reporred,including the rack ofscientific analysis in rhe reportingl the response ofparents; and rheimpact of thc rcduction in takc-up of rl.rc vacci.c on ['c nunrtrcr of cuscs of mcasrcs,mumps and rubella, including their worst side_effecrs.

pages 116-119

1 . t is uansmitted lrom one pcrson ro anorher by droplct inlccrion.' It can aflect a wide variery oftissues, bur pardcularly infecrs rhc lungs rvhich means it. is easily coughed out and spread.

' It has evolved a protective wax outer covering.This allows bacteria with the randommulalion rvhich providcs thc tirickcst ourcr co:.lr roror vcars unr'trre nort i. i,' a ro,v phvsicarc;;r',J:li,,lrT':::::.Til;'jJ""'*'trcsponsc, at which point thc hrcrcriu can trkc Ir,ll,l rncl bcu,rmc ire rivc.f1165g bactcriabcst {incd for surv.ival in drcsc co.rliLions ura t]," un", rv'iclr rvill bc passcd on.

' Anacks the immune system of the host and so red.uces d-re delences against it.' * has evolved resistance to mxny of the most commonly used antibiotics, rvhich meansit is more successful at surviving and spreading easily.

2 Primary infecrion: oftcn sl,rnpromless but causes an inflammatory response from theimmune system.The immune response forms a mass "rrirr;.-;;il;;;;;il,.,;,-dead bacteria and macrophages uapped in the cenue u,here conditions are completeryanaerobic After about cigrrt wecks trrc immunc systcm controls the mycobacteria, theinflammarion dies down and the lung dssue heals. urL ilrvcuoacterlar

Active rubcrcurosis: the bacteria mrrlriply r*pidiy ancl dcstrpy r'c )ung tisstjc. symptomsincludc fever, night sweats, loss of appetite, loss of weighr, fcciing tired and listless. As rheinfecdon invades rhe lungs, it causes a cough. As r-h. clugh ,"._";r., ".

Uil.:; ".

Iungs bccomes damaged and btood may be coughed "oln *" ,;;;;;;.,;";*.,

the tungs is stead'v destroyed, rvith the arvcoli b-rcaking dorvn to ,ril;;;;., ;.r'.,.n,air spaces_TheT cells of the immune sysrem are ,ff".,.0 so antrbody producdon isrcduccd' Evcntua'yTB causcs dcarh, ciLhcr bccausc Lhc inciiviaLrar c'.nor gcr cnoughoxygen from the air tluough their damaged lungs, their organs f ail *Lrough lack ofnutririon, or *rough opporrunistic infections such as pneumonia.

Edcxccl A2 Biology Implemenbtion and Asscssmcnt Guidc forTeachcrs and Technicians Opcarson Educadon Limired 2009

,_: .:::

3 [S+C] Thevalid.

. Povcrty: malnutrition thcrcfore supprcssed immune svstems making infection easier,

. Crowded living and r.vorking conditions: ease of infccrion.

' High rates of illncss frorn malaria, watcr-bornc discases ctc, so immune system undcrprcssure.

' High rates of HIV/AIDS so the immune sysrem is inacdvared, making opportunisticinfecrion easicr.

' Poor infrastrucrurc and limitcd mcdical rcsourccs, so lack of vaccination programmcs,lack of accuratc diagnosis and lack of drugs r.o tlcat symptoms cffectiveiy for the dmcrequircd.

. Catlc infectcd wi*r bovineTB and milk not pastcuriscd.

4 [S+C] Thc ansrvcrs should includc sorrc or al] of ti-rc following.

Any valid points, well-argucd and rvell-rcsearchcd matcrial, showing awareness of theconflicring perspcctives of scicnlisrs, farmcrs, poliricians, tlre general public etc.

pages 12O-'123

1 Initially alier infccrion pcople may have lcvers, hcadaches, riredness, and swollen glands

but may have no symptoms. About 3-12 wecks after infecrion, HIV antibodies appearin the blood so person is I-{IV posirivc. oncc rhe infecrion is esrablished, au symptomsdisappear and this stagc may lasr many years (in fit young people with access to effectiveanri-AIDS drugs), or months to years (people with litrlc food or medicine).

During dtis sragc drc virus rcplicutcs, infccr-jng drc CD4-l:hclpcr cclls but is kcpt in cficckby drcT killer celis.This is rhc sragc whcn othcr peoplc may bccome infccred *uoughhlgh-risk behaviour. E*cnrualiy secondary infcctions devclop as the irnmune sysrembegins to be overwhelmcd and symptomaric disease returns.The viral load becomes solarge rhat the immune system can no longer cope.The normalr:heiper cell count fallsIiorl 500 pcr mnr3 of biood ro about 200 pcr rn*3, and symptoms devclop includingweight ioss, fatiguc, diarrhoea, nighr swcnrs and low-gradc infections such as t]rush.Thisrapidly progrcsscs to the final stage.

As thcT:hclpcr ccll numbcrs fall, scvcrc symploms bcgin to appcar such as major weightloss, dementia as brain cclls bccome infecrcd, canccrs (e,g. Kaposi's sarcoma) and seriousinfections such asTB and cryptococcal mcningiris.These scrious diseases, along withopporLunistic infection, such as pncumonia lead to dcarh.

klc:ccl A2 Iliology Irnplcrr,r :tation and Asscsvncnt Guidc for-I.rcbc:! :nd Tcchnicjans opcarson Educadon Lii, :.d 2oo9

TB: Bacterial; infec* a wide range of cells, including lungs, lymph and bone, as welias macrophages of the irrvi&inthe,";,,0"..;;-:!:!:#Til;lili.iiff

:::,"J:T:fi :J.",".:,"?,,fi ;'.",',::ilfi#.::;:::,::,0'-*'to rungs o. -^rn,,t irio,, but arso reaves body oo",,,ocured by anribiorics;.r.i'#:T.T;*;iTffiilcm; can bc trcotea effecuverv anrl

HIV/AIDS:Viral; infects the helpcrT ccils of trre immune sv*^tr. ori^- :_:^i , . -pcriod rcmains dormant rvirhin rhc inrnrunc ,rr,",r, ,.lun. systcm; afler initial infecrion

a pardcurar ser of svmproms bur rhemain imiacris J;:H:::,i1.iilil;iilll1,vulnerable to a w'ide range of opporrunisdc inlections which usuai)y resurt in death; thecourse of disease can be slowed bur nor prevenred uv *.oi.uJo,i'; il ;:;;.,,*vaccine.

3 Main mechanisms: rhe rhick coat of M. ttberutbsiscnabies *rem ro survive ins.idemacrophages for many orrtl '.n.r

dormant o, ,10*-g.o,uing srarc.This is the resu* of;:l:::::T,"T::,_.,*.?"

thickcsr coars survivc aJd wiil be abrc ro inrect other hosts,

evolution. :ssful pathogcns. Multidrug-rcsrstant srrains are also the result of

ltfiTf.Htil.T:(and rhcrctbrc cvolurion) mcan changcs in arrtigens which makes

immune svstem reduce'"T:lr:iil.T,:"#;::},i virus' The targetting ."u, or J.

' antigens makes vaccine productio' very dilficult. fighting the virus' Rapidly evolving

Some pcople have genes which make thcm rcsistant ro Hrv. Jn counries where the

:iffi: :T:,::::::*' wil bccome oo,-,.in"ni i* u'iopuradon as individuars with them

, fU::,

Thc answers should include somc or all of rJle fot)orving. Orhcr points may be

Edcxcer A2 Biorogy rmplemcn.rion and Assessmeot Guide forTachers 3nd rechnici!ns opqrson Educetion Limiicd 2009

Pages 128-129

{ lj It supplics energy in thc forrn of ATP lor all ccllular reacdons. ft also supplies subsrates- for othcr metabolic pathways, inciuding amino acids and larty acids.

strcngths: succinct summary; sums up thc nccessary rcacrants, rhe desired product andrhc waste products; gi'cs a balance chcmical cquarion to shorv the proportions ofrhereaclion chemicals.

Limitations: shows it as a singlc reacdon, when it is a complcx series of reacdons; doesn,tshow wherc in the pr-ocgs-s ATP is made; gives no indrcarion of the enzymes involved;thcre is no indicaLig6*H@ff*{vc substrrles can bc uscd; thcrc is no mcndon ofhydrogen acceptors, coenzymes Etc.

Any other valid points.

pages 130-131

Q a Resliror.,"t"., *"ur.,r. carbon dioxide output and use rhat !o calculate oxygen uptakeduring respiration. Looking at the whole organism, ir gives an overall picture but nodetail olwhat is happening in individual cells, e,g. u,herhcr the carbon dioxide comesfrom aerobic or anacrobic rcspiradon. Any orhcr valid point.

A-'{ (T) lfne apparatus rvith rire two tubcs rvill givc morc rcliablc cvidence bccausc rhere is:

* " "

clcar scale to mcasurc changcsl syringe for recafibiarion; KOH on bot]-r sides toeliminatc drc amount of carbon dioxidc in normal air lrom the results. Anv orher validpoinls.

@ Euidan." is ncedcd to associatc rhc subsrrare molcculcs or enzymes involved in aparticular stage olrespiration wi*r the mcmbrancs or the contents of a pardcular area ofa mitochondrion, e.g blocking or poisoning of one mechanism and observing the build-up of product in a parricular arca of the roitochondrion.

pages'132-135' 1 During vigorous cxcrcisc, tnusclcs rcspirc anacrobically, producing lactare which builds

up in muscles and is carricd arvay in the blood.Whcn cxcrcise stops, as well as thenormal oxygcn dcmands of the body, lactate must also be oxidised 1o pyruvate andg)ucosc in thc livcr,,{f i'] and phosphocrearinc rcvcrs nced to be ,"rro..d, myogrobioneeds rcoxygenaring, and metabolic rcaction ratcs are faster due to raised temperalureusing more ATP. So r-he oxygen demands of thc body rcmain high for some time afterthe complction of the excrcisc.'l'hc rare of brearhing continucs to be raised to suppiythe necds of the body and t.he hcart ratc rcmains high to pump extra oxygenared bloodaround rirc body and rcmovc thc cxccss carbon dioxidc.

2 Diagram similar to fig.7.1.6 wirli anr.loradons such as rhc follorving. Glucosc, 6C sr:gar, is starring point.. ATp uscd ro phospl.rorylarc glucose _ 2 phospharc groups added to give

phosphorylared 6C sugar, onc reacLion conrrollcd by pi:,osphofructokinase, rare-corlLrolrirg rcacLior: Iirr l.c wrrorc proccss of cctular rcspiraLion.

' Phosphorylated 6C sugar split to form 2 moleculcs of 3C glyceraldehyde-3-phosphare(GALP).

rdc-\ccl '\2 Biologv lmplcmcnlarion and Asscssrrrcr:' Guidc iorTiachcrs andrcchnicians opcar , r Educarion Limircd 2o09W

Each molecule of GALp converrcd to pyruvic acid in a serics of steps _ lor eachmolecule of GALp 2 hydrogen aroms removed to reduceclecuon uur.f../t "r*..1; ":,.,"-

NAD which is passed along:i':T'"r:::;i'Jf :T:::11""-toproduce'-",..'l-,'"Lirl,1'::'HlT?:,i::The i'irial phosphorylarion reacdons arc reversed before rhe finar intermediare is

;#H},," pyruvlrl.c ancl drc |)rosp)rirtc grou]) ,.t.,,r..t ;, usecl ro proclucc A1_l)

2 molecules ofpyruvate enter mitochondrion and go into Krebs cycle for everyglucose molecu.le rvhich enters glycolysis.. If insufficient oxygen, plruvate con,.,rrteC to lectatc o: erhlnrl

3 During the proccss trvo hydrogcn atonrs arc rcmovcd from r'c 3C sugars and taken upby NAD to form reduced NAD rvhich ,f_,.n .nr.r, ,fenergv which is used to phosphorvrate 3 .or..ur.r;;;s;T;;il:i';:T il:H*rvhen rie 3c sugar is converred to pyruvate. This rcplaces thc ATp uscd up to prime rhe6C sugar, and the remaindcr is available o, ur"iui.n".r^;" :,::^:^,::,:p

,o p,

that the substa,. -.r.. on into acrobic respirat.ion. crgy lbr ccll metabolism, assuming

pages 136_137

1 Giycorysis: doesn't need oxygen ro produce ATp; linear; rerarivcry simpre; takes prace incyroplasm. Any othe r valid point.Krebs cycle: needs oxygcn

ll.produ.." ATp; cyclical; complcx; rakcs place inmirochondria. Any odter valid point.

2 IGcbs cycle alonc docs rc y c r e d ucc r y p ro cl u c e s J:i; ir,T: :ffi?; fl : ::i

,-: : ::1,,.:: lllill ti,li Xh filli

H::::::*il':;Hn:'"'o"t chain' which in turn rereascs encrsv rhar is used to drive

I tS+Cl The ansrver should includc somc or all of thcvalid. ,lLruuc somc or ail ot thc following. other points may.be

Itebs used enzyme inhit.re s u r rin g i n a bur a -up il"J:.,".:::: ;ff :11: ;.ffil;; il :1":: ;S:#**comparcd to an anarysis of the normal process..This cnablecl Krebs and his team ofscjcndsts to work out exacdy rvhich chcmicals r*i"*,*u in a particular stcp of thcprocess. Answer could include diagram of appa.arus used.

pages 138_14.1

t ::;",

The ansrver should include somc or all ol the follorving. Other points may be

Diagram should show all stages of aerobic rcspiration: grycolysis, link reaction, Krebscyclc and elecFon transport cl.rain, making al"r, ,ulor.u sed and formed, *r,lr.?ar,."a NaD and ..or.J'o;3,,.:lH,Jfi :ff

t..?':::r.

iHil:iil :: I.ffi :.::,r; i:::f:$::ii1 inai.",,.n ",

n"; ;;;; ;; -,,diagram is important. bc inclutlcd' clariry of layout of

Edexccl A2 Biology lmptcmenetion and Assessmcnt Guide forTeachcrs e ,d Tcchnjcians Op.arson Educarion Lihilcd 2009

2 The oxidation ol glucose is a muiri-stcp process during rvlrich rhe glucose molccule is

splir inro 3C unirs, builr back into 6C mole cules and thcn dismanded again. As hydr.. ;.,

is rcmoved, it is used to reduce carrier moiccuies that pass to dre clecuon transport ei:,':;r.

As the components of the chain are reduced and then oxidised again sufficient energy

. is releascd to drive thc production of A"I'P. By the end of rhe process glucose has bee n

complctcly oxidiscd to crrbon dioxidc and rvatcr.

3 Glycolysis (at the start of acrobic and anaerobic rcspiration) has to expend ATP to move

re duccd NAD into the mitochondria to reach the electron transport chdin; one hydrogen

is removed frorr cach 3C sugar in glycolysis,while 5 hydrogen atoms are passed into

thc clecron uansport chain from each 3C pyruvare molccule that enters the Krebs cycle

(acrobic respiration only); acrobic rcspiration involvcs completc oxidadon of glucosc

while anaerobic resuhs only in its partial breakdown. Any other valid points.

4 Energy from electrons as thcy pass alcng the clecuon uansport chain is used to

acrively transport hydrogen ions into thc space bewcen the inner and outer mitochondrial

membranes.The hydrogen ions cannot pass through dre jnncr mitochondrial membranes.

So a conccnualion gradienr lbr hydrogcn ions is buih up ilcross rlrc inncr membrane.Thisalso creates a pI{ gradient and an clccuochcmical gradient. Aldrough there is a tendency

for drc hydrogen ions to movc back into thc mauix, thc only way thcy can move back is

*rrough special pores.Thesc porcs arc found on dre sralkcd parriclcs, and ihe movement ofthc hydrcgcn ions *Lrough drc porcs is iinkcd to an{l'Pasc cnzyme.The cnergy ftom thc

gradients is used to drive rhe synthesis of ATP. This modcl is important because it provide,

a mechanism for the observed cvcnts in a rvide variety of cells, and it shorvs how the removai

of hydrogcn atoms from glucosc molcculcs can rcsult in the production oIATP

Edcrccl l'.: iIi.logl,ImplemcnlaLior, and Assessmcnr ( L dc forTcrchcrs indTccluicians OPcrrsoii Jliiucadon Limircd 2009

ffi

Pages 142-143

1 vhole muscle is made u p of m any mus clc fibre s. Difrere nt libres :night have differentduesholds for response, or dirfercnt levels oiresponse, so whcn the rvhore muscle isstimulated the contracdon might be more or less than expccted.

jages 144-147

'4 'J l::bit respiration takes place in rhe mitochondria supplying thc acrive muscle cells with" A I I' as an energy supply. Myoglobin is a protein similar to haemoglobin, with one chain

rarher than four, rvhich binds oxygen ancJ has a much highcr affinity for oxygen thanhacmoglobin' Myoglobin readiiy acccprs oxygcn fronr drc blood und acrs o, on.r^r.g.,,store in *re musclcs.

. e Fast rwirch fibres havc ic,.-m1,'c!og: and liulc myoglobin: rhcy produce a quick burstft o[ aerobic energy then anaerobic respriition conrinues: rhey farigue qui.tty. sto* wit.hfibres have many mirochondria and plcnty of myoglobin; rend to have a rich blood supplybringing oxygen which is taken r-rp and srored by the myogrobin; atow plenry of aerobicrespiration over Lime .

ps9 Lee muscles contain lots of srorv nvitch fibrcs, wirh a good brood suppry and lots of^' myoglobin. Therefore these muscres are a dark colour, contain lots of mitochondria

and so provide sustained activity for walking around but less speed and power in initialcontracdon. Breast meat contains more fast wvitch fibrcs, rviu\ rclatively little myoglobinand lew blood vcsscls. Thcrcfore drcy arc a palc colour, goocl for short cxplosive bursts ofacdvity such as a shorr flight.

Striated muscle 5mooth muscle Cardiac muscle

attached to the skeleton not atiached to skeieton not attached to skeleton

involved in locomotion involved in moving foodthrough gut, controlting

diameter of blood vessels etc.

pumps btood out of heartaround lungs and body

controlled by vo{untary neruoussvstem

controLLed by involuntaryneryou5 System

ccntracts spontaneously, somevoLuntary and involuntarycontrol

striated appearance undermicroscope

no striations seen undermicroscope

striations with cross

connections seen undermicroscope

contracts rapidly contracts slowly average around 70 contractionsa minute

fatigues rapidly latigues slowly does nct fatigue

Edexcel A2 Biology lmplemcnlation and Asscsrncn! cuidc forTeichrs rnd']'cclmicirns opearsod Ed,ucaliotr Limitcd 2009

'{ tS+Cl'lhcansrvcrshouldincluclesomeorallofthefol)ouing.Orherpointsmaybegalid

5[ow twitch muscles Fast twitch muscles

deep red (lots of myogiobin) pate pinUwhite (little myogtobin)

lots of capiltaries few capiLlaries

{ots of myoglobin to store oxygen little myoglobin

not much stored glycogen large gLycogen stores

littLe sarcoplasmic reticulum lots of sarcoplasmic reticulum

doesn't fatigue easily fatigue easily

many mitochondria relatively few mitochondria

P€ges 148-149

L Diagrams as in fig. 7 .2.7, fully labcllcd to show rhe H zone, I bands, A band,Z lines, actin

and myosin {llamcnts.

2 Calcium ions rclcased in rcsponsc to nervous srimulation o[the muscie set up conuaclionof thc sarcomcres. Calcium ions bind to uoponin changing rJre shape of thc molecule.This changes t1-rc shapc of the ropouin mo)eculcs, so'&cy pull on *re tropomyosinmolecuies ro which they are arrached.T'his moves the ropomyosin arvay from lhemyosin binding sites on the acrin moleculcs, exposing rhcm, so thar rhey can bind withthe myosin heads which sets up the conuaction. Calcium ions aiso needed for the acdonof *re ATPasc enzyme in tfrc myosin he ads, rvhich e nables rhe heads ro renJrn to thcirresting position.

3 a ATPbindstorhemyoglobinhcad,andthereleascofenergywhenitishydrolysedailows rhc hcad to rcturn ro rhc rcsling posirion.Thc bonding of the ADp and

- iroganic Bhosphate results in changes in the shape of rhe myosin head so it can bindto the actin binding sitc.The release of rhe ADp and inorganic phosphate resuhs inanother shapc change rvhich rcsults in lhe rclcase of the myosin head from the actinbinding sitc. AfP is also nccdcd as drc crrcrgy supply for rhc carciurn pump wrrichreturns calcium ions to the sarcoplasmic rcticulum, ending the contraction.

b [s+ c] The answer should includc some or ail of thc follorving. other points may bevalid.

Aftcr death, once there is no more ATP, the myosin heads cannot returftto the restingposition but remain lockcd upright, so rhc muscre bccomcs stiff and rigid.

pages'150-151

C SVnovial fluid is produccd by synovial rnentbrancs i. joinrs *,ith biggesr range ofmovement. It acts as a lubricant bctrvcen thc cartilage covcring thc ends of the bones.Prcvcnts wcar and tcar o[ *rc crrriirgc.

l'jdcxccl A2 Biologf Implcmcmation and Asscssmcnt Guidc fo.Tcachcrs anrlTcchnicians c)perrson llducarion Limilcd 2009

ffi_

/l ._,***"lwssec**liiiii?;ni#siffi#"{

.p 4 (:/' sones; form the lramework and support; hard, suong dssucl act as levers.' Ioinr".\,,L^-^ .--Joints: rvhere two bones mcet; ; allow movement.

ljii,fiT;Tiil.l:ff:::::"::lrhe joints;hord boncs in prace so rhey can douscful work withour becomins.""":;,'";,':;::':ru uonc.s rn ptace so they can do

the joint ro move -;;;;;:::"t":::l.l?,t^'.1, 1':'".:d to be erastic to auow J. i*., ",

the joint ro move ruh", n"."rJ^.." .,^;^:'^,::."tuu Lo oe elastic to allow the bones ,

tightness "r ";o;i;;;;;iliil':::::::]'::'-',"'::'".'lvcs

s,.c,,srh rvith crasticity;tightness of capsules varies r ' -r":r'L rrsstrc grvcs

r,. vrth movement needed in joint.

Muscles: provide the power ro move rhe joinrs; Ur_r. :;;attached to bones bv fenrJn.o rr,L,i^L r-.,,- conuact and relax; arei^tt:-'n"o

to bones by tendons *hr.h ;;t ;;;;;, i";l conuact and relax; are

is converled into moro*^., confaclion of the muscleff :J:T::fi"#J;:::: ::::: :1 i:Te."'sl; il, ;ffi :::::1,i:il::'::.muscle moves a bone in one t,dub as u.rey can onJy pull, so onbcne back to iis orisjn:l .,,":ir..,ion

and when ir rclaxes, anorher muscle puuc rhebcne back to iis orig.inal piace,

Any othcr valid descriptions, diagrams erc

Edexccl A2 Biology Implcmcnurion ud Assessmenr Cuidc forTeachc.s qnd Tcchnicirns Oparson Education Limitcd 2OO9

ri:]i!"':i+i

Pages 1 52-1 53

1 The natural pacemaker should send impulscs regu)ariy through rhe conductivedssue of*rc hcart to thc vcntriclcs ro rigger thcm to conuact and pump blood out of the heart tothe lungs and around lhc body. I3y dclivering elecuic shock to the ventricles when the SAnode fails, thc artificial pacemakcr uiggcrs conrraction in rhe ventricles and replicares theintrinsic rhy*rmiciry of thc hcart bcat.

2 P wave: clccuical impulscs uavelling from SA nodc.

QRS complcx: wave of excitaLion spreads from rhe AV node *rough the bundle of His

and through the ventricies.

T wavc: recovcry of contrrcrilc tissue and rhc vcnuiclcr.

pages 1 54-1 57

1 normal blood pressurc * cxercisc raises blood prcssure - baroreceptors in carotid arteries

detect rise in blood prcssurc * barorcceptors send ncrvc impulses to cardiovascuiar centre

in brain - ccrdiov'Jscul?r ccrtuc scnds ncrvc irnpulscs to hcart and blood vessels + heart

ratc slorvs and blood vesscls dilate - blood prcssure fails back to normal.

7 rcsl excrcise re(overy

10

70

:i

€5 ro

5

3a1 6000

14000

12O00

10000

800

500

400

?oa

0

Time/minutes

At rest

o"r* r.*l*ob".{-tt".".rt.r+' +t *€-".b ^S' v*. <c" *d

.,C \n' .I? os

"+*Blood ftow at r€st

14000

'12000

10000

800

600

400

200

0

Vigorous exercise

fmm-Fn-ls ffiffi

Cr'.i_*+'".|'''{o-{.,o"o;ir"e

^,." \$ .g$ o"'

qY

Elood flow during vigbrous mrcise

I heart

ffi tiver

Sl adren4l g{ands

$ brain

frl tung tissue

El kidneys

&l skeletal musclcs

[ 5kin

fi other parts

il hearrEl liverS adrenal glands

Sl brain

B! lung ti$uel-i'l kidnevs

El skeletal rnutcles

El siin

$l other parr

Edcxccl A2 Biology lmplemcntaoon md Asscssme nt Guidc for'lerchcrs md'ltclnicians opcrrson Edusdon Lifrited 2oo9

During exercise thnow ro rhe *r r;::,T:i:;:*:".ii:::::; :,i

the b,ood supp,y is shifted rheimporraut. BlcoJ s

;:H T:,J:,"T_ :::m*,,.#ffi j ffi i H:::

ffi n:Tff l.i,'bloo j o.* ;;;; illilT|";,::T::: :T:J: "",ood

and ";;;; ;;;J, ." othe skin also increases *."r,","1"^^.*^rr:ure

oxygen into the body,. Blood florv tob,ood ,o ,.,' -l*lll.'.T;ii#::*:.lllJ il;,ll':.J; ffi il".',,I,. ,"o,.

4 Nervous controi: involtn_ervcs srow ir down; n.'ntutt'

sympathetic ncrvcs specd up herrt rare, parasympathericlflccr *rc aO*

""O r"l."es

come from cardiovascu

cardiovascurar ".nrr" i.h"nr"

*. .nrur- o"ii dJalar ccnrc; impuiscs lrom Lhese nerves

rv hi c h a r e a rre c r e d o, ;,0;": ;.1T: :,: :_.:_,..:,1 il, :;: l,:: : il: n"j ff : "

t ;baroreceptors r..r*.;l;;;J..Iffi ffi'#:.l,.".l"

hearr as .*"..i.",,".* o.,.0.,irnportant as exercise;;,;;,;,,'-:"'":::::::'n !h,: n::k,rvhich is parricurarryheart rate il;il. j:ffi:::Jt**::surc carbon dio*',. ,,' *. ol"io'"i," .o..,Voluntary conLrol: nervct'e sAN.

- '^-' ' JS from conscious parts of rhe brain can arso srimulate or inhibirHormonal conrol ;adrehcarr so it bears faster.rnt"n.

stimurarcs rhc SAI{. s

Anv othcr varid points td more '";';;;;;;:'l"i';i:lrlr;:'""'"" rarc ortre

pages 158_161

I Spiromctcrs can bc uscd [o mr,rcrr",, tr,.. r.__ .tAlso, r-he r'*r; ;;"

"t:mcasurc

$s lrrcadring I'rt

2 IS+cl The answer rnor""ount'n'o'"'*' *'u'i'":t:'l':..::

arr'l rvhilsr cxercising etc'

D agram shou,a in.,ude ife;::::j:ffi: ;:::d-: ;il"-::-':::,,,.:i, *il ;m :; : :;H t* :i:i1;ii:T: T,;

';:'"T; ill+ri: : lTffi

. r d b. d e s

cnuoned dircctJy or by association.

Edcrcer 42 Biorogy Imprcmenkrion and Asscssmeor cuide for,oachcrs rnci rechnicians opea.son Education Limired 2009

id!:i

3CarbondioxidelevelsintlcbloodincreascrvithexerciscaSmorecellularrespirationrakes place (and pH levcli lvhich fail as carbon dioxidc concenuarion goes up) and fall

ashardbreathingcontinuesafterexercise.l-evelsaredetectedbychemoreceptorsindre

hindbrain, rhc carotid bodics in tl'rc carotid artcrics oltirc ncck and the aortic bodies in

rhcaorta'Tlreyrcspondtochangesinlcvclsbychangingdrcratcofimpulsessenttotherespirarory cenue in the brain, rvhich in turn send impulses to *re intercostals muscles

uni th. dirphragm to change the rate and dcp*r of breathing'

Brain cortex: recognises movcment has begun and srimulates the respiratory cen[e to

cause an increasc in brcathing rate'

Suctch rcceptors in musclcs rcgistcr movcmcnt) and in thc lungs mcasure the dcgree of

stretching,andrespondwirhimpulsestotherespiiatorycenfetoaffectbreathingrare'

Voluntarynefvescanbcusedtoincrcascordccreascratcordepthofbreathingwithinboundaries, beyond which the normal breathing reflcx kicks in'

Any otJrcr valid suggcstions

4tS+Cl.lleeansrvershouldinc]udcSomcola]lolrhciollow.ing.otherpointsmaybevalid.

For:bcstwaytocollcctdatatohc.lprvirhucetihgbrcathirrgproblcmsinotherchi]dren;Iesponseinchildrenisdifferentrotheresponseinaduits,socan'texuapolatelromadultsro chilclrcn; children involvcd enjoyed rhe expcrience (aud probably got a lot from ir)'

Against: could have bcen v.cry risky - not right to put children at risk urulecessariiy; they

rvcrcn't benefitting dircctJy {iom rhc rcscarch so not a good reason to do it; conditions

wcre cxlreme and onc chiid srugglcd with thcm'

pages 162-163

lMctabolicreacdonsproduccheat.Duringcxerciserhe}evelofaerobicandanaerobicrespiration in dre muscles incteases so the amoun! of hear produced increases

considerably. High temperatures can denature cruymes and damage the metabolic

proccsscs thcy control. Maintcnancc oI rciltivcly conslant internal tcmperature by

swcaling, skin flushing and so on is vital to prevent the core body tcmperature from

risingtohighcriticallevelswhenpositivefeedbackmechanismsrespondbyincreasingthe metabolic rate so proclucing even more heat and m:king temperature rise until it may

rcach lcthal lcvcls'

2[S+c].lhcanswershou]dincludcsomcorallolthefollowing,otirerpointsmaybevalid.

Srengths:givesdircctevidcnceofindividualhumanrespclnsetochanginglempelarure;can control conclitions qurrc closcly so thet rcsults clcarly indicatc cffect ol changing

condidons.

Weaknesses: not parricularly comfortablc for person bcing studied; takes a long time to

cojlcctdataonalargcnumbcrofincjividualsinmanydilfcrentconditionsinorderto

Produce rcliable conclusions'

ISdcxccl A2 Biology lnplcmcnrarion anrl Asscssmcnt Guidc for'llrch$s andTccluricirns oPcarsolr EiluceLion Limited 2009

pages 164_167

t llilTj::J,".,,T:Tj:j:i:,:j.:llerarure,wu increase due ro muscre activiry and

;::: :: j :::: ::1 I*' 1* rc e d b a ck ;. ;' ;; ; ;;:: :

j: J::::,1' il'J, ;heat lost through evaporation, and irng so

".";";;;;";"" ifill};r"* increased blood flow to surrace orskin means

"n.*,o*

. Drinking ice cold water can cause problems because ut, ,.,_ra, to drop the blood

ilTil:*:il i.#::::: :11 i:':: p'o'r u.."'r bv mu scrcs'"u n*"'

"'"i""1*.,,..reduce hear,",. or,,*,,',jl::T:"ffi."rH?J;:::""'"'.rion orbrood vcssers in skin rorise again as a res,* of themetabolic heat so the rrr;::Tr:T::ili:::l;:::::.:but it wr'uid take ir-:ngcr to rcstore rormal core body tempcrarurc. Any other valid points.2 Thermoreguladon is not as effective in elderly peopre.as brood circularion may be poor.34'c is a hilh temperarure and so rhc man *'i ,oo, gct hot borh from the externartemperature and the exercise. A raised externar ,"*f

".orr." makes it harder to losc bodyhear rhrough conducrion' He couid n"* o-Jt.-, iirh thc negadve feedback sysrem asproronged walking means.prolongcd e*..rs h..t frocu..a by muscres. Also, ror rhc dog- exercising in heat wi*r thick rur coar can r."a ,J o"".n"*ting as rimitcd area for hear Iossrhrough sweat. Any orher valid points.

3 Negadve feedback: core temperature incrcases, srveaL.evaporadon and a.erioie shunt opens ,o ,r;u;;;-,Jf ,ffffi?'J"li.'.T:.r';..rr*",heat is lost by radiation and conducdon ,na "o..

,..,icore remperarure down, ;;;;:,.,, ;_ffi * :::::':::::H:T::,closcs so less blood flows near *rc surfacc of thc skin rcducing hcat ross by radiation andconduclion, core temperatura ,ira, ro*u.d, n"a_O arr,..Posirive fcedback: core rerwirh increase ; ";;;,J:'J;:;l"J:,iXl:'j::]]*.',

metaboric reacrions speed upra te of metaboric reactions fur ther, in crudi ng

"; ;;::T;:"Ti: ;I:l:il,:r.. ""

5.'. i:!:r.':: !i5_:.1.:l

".i.l t!ij:.4:i:;3.j{r'i: a:.:.;-:.a4

Pages 168-169

1 tS+Cl The ansrvers should include some or all of rhe following. Other poins may be

valid.

Fig. 7.4.1 shows dara lrom rhe National Statistics site collected as part of a Health Survey

lor England.The samplc size is very large (ovcr i4 000 adults in 2003) so the evidence is

rcl iablc.

The obcsiry data for frg.].4.2 came from a study by the International ObesityThskForce

in 2002, and rhe cycling dara from drc Departrnent forTransport in 1996.These graphs

summarisc large-scale intcrnarional and nauonai srudics, and are considered convincing

evrdcnce.

The pie charr in fig.7.4.3 is bascd on data of ail newly diagnosed cases of diabetes in the

US, and again is a large sample sizc.

The graph in fig 7.4.3 comcs from Narional Institute of Aging in the US, with a sample

' size of abour 1000 people, all ofrvhom rvcre overweight and had slightly raised blood

glucose leveis, both ofwhich are good predictors for the development ofType 2 diaberes.

45% of rhe sample came lrom parricular minoiiry groups known to have a higher risk of

developing d.iabetes.Thc survey compared this group rvho increased their level oi activiry

rvith orhers rvho eirher receive d drug ucarncnts or placcbos. Sample size is relatively

small here, bccause of thc breakdown by agc, and the cffcct of ethnic origin might mean

that thcsc rcsults arcn't as valid for othcr cthnic groups.

2 tS+Cl The answcrs shoultl include soms or all ol thc following. Other points may bc valid.

Correlation is when facrors vary in a similar way, either direcdy (going up and down at

the same time) or indirectly (one going up as thc othcr gocs dorvn and vice versa).This

suggcsts a link benveen the factors, e.g. something else might be affecting the factors

in thc same way. Causation is rvhen a change in one factor leads to a change in another

factor. A vulid mcciranism is ncedcd to cxplain thc causal link between thcm.

Much of the evidcncc for a rciarionship bet*'een level of exercise, obesiry diabetes

and heart diseasc is in dre form ofcorrclation, as shorvn by the figures on rhese pages.

Incrcasingly drough, scicntihc rcscarch is producing cvidcncc of causal links, c.g. that

moderare exercise sucngthens the heart and circulatory system, so reducing the risk of

heart disease. A causal link wirh obesity is more difficult to shorv because many sudies

ignore the impact of fitness rvhich may be grcater than simple BML

pages 170-171

1a 8000moderaresrvimmers:largesample; inspiteofopenagerange)sizeofsampleincreases validiry and reliability.

231I,35-37 year old marathon runncrs: big sample and clear{y defined age rangc

incrcascs validity and rcliability.

750, 40-8 1 runners: rcladvely large sample with defined, if large, age range.

b Thc answers shouid include some or all of the following. Other points may be valid.

10 men running for three wecks: tiny sampie, all one gender, vcry short time scalc.

16,60-72 ycar olds modcrate excrcisc: small sample, gcnder not dcFned.

lirlexcel A2 lliology lrnplemotation and Assessmeot Guidc for-lcrchers andTcclnicius OPcarsorr llducation Limitcd 2009

$, " l::*dies seem ro confirm thc hypothcsis thar rimmune system shown by rcducing the incidc:,cc ::::T

cxcrcise benefits thto suggcst stronslv. nnrr nn. l^.." ..,-..- , , olURTIs' tt-;; ;;r..Jto suggcst strongly, and onc lcss srro'gly, ur;;;;;#"t

ls' .Light sudies seemimmune svstem as measurerl .; i"-";'^'^i:::::::*: exercise is damaging to the

o,r.:", rhe answers,;J.Til.:::T :l,Y,t|l'.i,.(

'alid. rur1rtr ur arl oI the.foilowing. other points may be

In order to show causation, there needs to be eithmany large-scale and reliable studies o. il;J: ovcrwhclming ei'idence from

from scientific research. currentJy neirher of thes]s to be a clear causal [n-k cstablishcd

suggest that one day a causai rin-k is rvorth ,"o*"*trlrlu'"able, although the data

pages 172-123

1 P wave: clccuical impulses favellino frn_ e ^

_^r,

n:*H*::iltr,...,*;i:"ii:J:1";::T:ilff o".li*"*."0valve opcns ,;;;;;;;,t"venricular

valve closes' vcntricics ,,rr,.".or"-il'*'""r,,"T wave : repor aris ation "il:::l,T. ::::: :: : il::.;.:iiil:it.T:::ff ::Til:,:: ffi:,J,r;i:T.1 {, ; ff ,.,h e rva y,h e

ALrial fibr.rarion: auia bea normei rhyrhm of rrre hcarr.

Incrcascs ;;;il ffi;;::: 1':': inerfectivcrv; don't nli and emprv properly.eff ective,yr,,;;.:;;;,ili],:ilJi*":,|]ffi

:",f ,ff :,,,"::.Ji;;;;,Vennicular fibrijlarion: vcnrricles ., ,rr. ,,..rt' ir. *.ir'nrr*, no longer conrracttogcthcr, conrracr erradcally and weakJy. Littre brood ,, :il#:T.t:ns€r conrract

causes a rapid fall in blood ore*.,,"" ",::,;,-::J':"".tt pumped into the arteries which

Of,.n l.rdr-;; *'#.; pressure, starving the brain, body and ,;";;;;;;;:..

an elecric shock from , O"ii.lill;r.mcdmes normal hea.r .r,v,r,..*"i" ,.ri.ii. O,

pages 17L177I a Il ostcoarthritis the cz

; o i n,, u.. on'. I ;;;;.lff :il}:: ;:"#,il [.J'u... o,.,, o n a n d c u s h j on s th e

membrane m.k., mo.. fluid so the join, ;;:il, ;:tt cnds thicken and the svnoviar

The rvhole ;.i", """ u.."-. #;]::::'l:": :T the joint capsule thickens roo.awa y c o m p r e t er, .

" o ;'."il'" :':: r','.o"l:rr. ill"J "l:::*.,,, "

" .,. u,,s"' *;;,,

" ;:lT;"il".":H ffij:*: #:'T.;t#il:' s'[a*s to rvear awav as we',

valid. , _-_ ...!:sur ' ,,!r or ar ol the fcllowing. otlrer points may be

In People over 40, osteoartlurornrs and possibtv rt .

"nn., Ltit^i.l-::::ll' lt

result of vears of rvear and rear on rlejoints and possibly rt,..n .t 'r qoual} urc resull of years ofrvear and tear on t1-,e

of osteoarrhritis develonino ":i ::T::i:ies. Being ovcn'cight increases ,h.;;;..ofosteoarrhritis develooing a

"'/qrrlo'l "sttrg ovcnYcight ioccasionallv srrrrp. r-^* ^--

, ,,]n:r.aaras the stain on the joirrts.occasionally suffer from osreorrri,.ir;"--1"-::..:::"t on tne JorJrts. People unc:r 40

ei ther the,;J; ;; ;;;; .""T,?, *,:

::::y:11,"' *" knee rhis ;;;,;;,;;,either rhe resurt of a generi. .""0u,""',ir,;;irt:j::1".: *.', is armosr arways

consequence ofa tea, injurv in thc kne. \y/h-- ^^_-:r ,rcclivc Lissue, or as a delayed,il::H;I:,1lfi ilt:?,Jt*""::"Y:i$il:::il"r.*.:T:;l1t:jsurgicats ir is then a less erfe.,j". .;;i;; ;;; ;:ilil:..,::i.:.ffi:i::fil.

Edercel .^2 Bioroey rmpremenlation dd 'a'qJ nrt) ul.

Assessm€nr Cuide for Teichers rnd TccH hnicisns QPcarson Educrdon Limired 2o09

i':1

ii.!t

rl:r:I

2 a The answer should inciude some or all of rhe follorving. Other points may be valid.

Case history Z Case history 3

knee twisted foltowing tackle knee collapsed, no contact

much swelling around knee joint knee swollen

joint tender joint painiui

sensation of something catching when knee

straightened

movement very painful

medial meniscus tear compleie rupture of anterior cruciate ligament(AcL)

Keyholc surgery: tlrrough a dny incision using fibre-opric tube with camera and

miniaturiscd instrunrcntsl thc drmagcd are'r is cut away so healing can occur; playcr

should be playing again wirhin days; no necd for radical surgery.

ACL: also uscs keyhole surgery; uscs graft of ligamcnts from patient or donorl needs

two rvceks rest to allow swelling to rcducc enough to do surgery "ttd

th.tr 9 monthsrecupcration and physio*rerapy.

In eidrer casc, an artificial knec would not providc thc same suength and flexibi.lity.

This ueatment is exccllent for patients rvith pain lrom osteoartluitis because they can

withstand some strain) c.g. that of moderate exercise. Top class athletes can't use them.

Thcy also have a finitc uscful time, whercas a wcll-repaired knee will last a lifetime"

Any other valid points.

[S+C] Thc answer should include some qr'all olthe follorving, Ot]rer points may be

valld.

The IAAF's ruling in 2007 banned the use of any devicc incorporating springs, wheels or

any other element that providcs rhe uscr with an advantage over another athlere not using

such a dcvicc.Thc ruling against Pistorius taking parr in rhc 2008 Olympics rvas bccausetests showed athlctes using the blades used lcss cnergy than ath.leres with legs to achieve

the samc speeds.

Some issues; Should prosthcscs be considcred.just from what they can do

biomechanically? Just because the prosthetic blades save energy, doesnlt necessarily mean

that the rest of the body is saving energy, because it isn't rvorking in exactly the same way

as someone with complcte legs, for cxamplc otl]er areas ol thc body may have to workharder to balancc.

If pcople using prosfictic limbs could all run tastcr tharlablc-bodicd athlctes, whcrc does

that lcavc olyinpic compcdtion?

If someone using prostheric limbs is able to compere on an equaFbasis with able-bodied

runners, would that relcgate the paralympics to a sccond-rate level of sport, particularlyfor those who couldn'r afford rhe prosrhcses?

Edexcel 42 Biology lmplemeotation and Asssstocm Guide forTiachers andTcchnicians ePcarson Educarioo Limired 2009

Pages 178_181

I Some,d-rugs, cah create ].11n11.q_

chinge in the body, eithcr increasing.physical .

3.i1T'*','*:i:T::'lf.T;:""1'.f :il.:,|,*.on.,,h,,.,"b.n,i.'d.*pr.,.ryare the ones fiat are ;anned onty during ""-o.oJ:::ttlv

excreted from the bodv. These

2 a [S+C] The answer should include some or all l

valid. t of the iollowing. Orher points may be

Genes that code for natural transcription factoran advantage in sport, and at competido. l.u"r l'such

as crydrropoiedn, can givewinning .ro .",-i"-,"* first. Thc pie ssure ," ,,:,"j1::1"

rhe difference between

methods like rhis tc . .vrn rs so grcar rhar using,narural,

b steroid hormoncs: il:ffi;:::ffiffir. verv tempring.

i:{"::i"l"J:*x*l ":j:...,. ffi rjil;i:l T":i=d;;'"i?,Ti,;;i.,'.il:*'.i;ilt;;ffi 3i*:*1i1::;ff : j"T:1:ruT*:;'";:ffi :;produced. qDiagral rikc fi g. 7.4. r 8,",,"i*, ol"?:,,J.ril?il,*bcrs

or enzymes

Pcptide hormones: do not enter the cell; bind romembrane-bound complex ,.,t*,", .'r*"& LU a receptor in the ccll mcmbrane; the

niggers a prorein kinase cascade rvhich involvcs',cr.si:1:::11 thc cell cvtoplasm and

proteins until the final product enrers dre nu.,"utt acttvadon of scveral different

switching or, ,r,. g.rr., linked to the synthesis orl unu acts as a rranscripdon factor,

(Diagram r*e nglz.a,zo in srudcnt d;,,;;;r:il*icular protein (enzyme).

3 a Possible answers include: the number of studentswas laken from (e.g. all cities, rural areas,0,rr..., "tutt"d; the areas rvhere dre surveysur vey; wh o run d e d rhe s ur vey ; d i d

". ;;;"; J:llT l?;Jll li,T :i.::.,"ffb It is inaccurate becar

use, how drug usc t,;:ff;l'ltrffi::,ffil? irit reflects rcgular use, on..-o',rythe sampres.were raken.crc (as givcn ,,, .rrr*".,o,jot ;:1. "t

t, doesn't indicate where

pages 182-.183

I The error bar on the left of the graph indicates a ranse of hFr.,,time (ge *i n g,ro*.r1 uni . d..;; ;;;il; ;;lf il:r,:ff :ffi :,:[:"ffi'JThe measured improvemenr in performance i";_;;;,bur rhar is similar to rhe errorrange' so living high and baining ro* *rr r.,u,irJ-ut. ri,,t. difrerence ro periormance.t ffi:,

T'hc answcrs should inclu<lc some or all of rhc follorving. Orher points may be

ll:,Lr.:,"", Orugs for proving pcrformancc should be allowed in sporr and somax-rmum red cell counr is not adequate ,, i, ,U"rvr]".,se of drugs.,F.elativist: setring a maximum tevel for total recl

"""0;;:*',:::^ , " .

Lt: rr.:

louoir is t.mptea to add to rhcir narurar .::l.t:"", is. rhe onry fair way to

damage rheir bodles using either hish_.rri;;.;ffiT::rilrffiwhere they might

Edexccl A2 Biology tmplemenmtion and Asscssminr Guidc fotTerihcrs and Gchnicianr opcarson Educarion Limircd 2009

Pages 1BB-'l89

,.'1 Ligl1r' nccdcd fgr photosynthcsis; important tlut shoots '.lrd leavcs move torvards itl roots''''

n".d io be in the soil so rcsponsc away from light hclps makc sure they grow in the right

direction; respond ro dir.egdon, intcnsity and length of c:i-posure'

0.rl:tty, grorfih movements of plant parts towards or arvay from the pull of graviry; roots

g-* ro*rra, $tu,ity.-s\rgp1s-qw4y;this helps to orientare the young plant as the seed

germinates below ground - shoots grow up, roots dorvn, rvhichever way up rhe seed is

-l^^, ^lpLdrrrru.

Chcmicals: p1ant. roots will grorv towartls somc chcmicals and away from orhers'

Water: roots grow towards rvuter in the soil; w'atcr nccdcd for growth'

&nLgr'qr..someplantsorpartsofplanrsrcspondtochangesintemperatureltheren,ryUarposirivcmovcmcnttowardslowcrlcmperaturc'e'g'manyrools'orparrsoftheplanrmayrespondtoprotectthecellsandtissues,e'g.Ihododendronleavescurlinthecoid; important ro help roots grorv in rhe right direcrion, and also 1o protect plant trssues

from damage in cxtrcmc cold'

Touch, rhigmouoplsm: plants (particulariy climbing plants) grow in rcsponsc to touch'

c.g. runncr bcans curving up cancs'

z'Plants respond ro srimuli by growth.They nccd to respond to sdmuli, such as direction

,nd int.nsity of light, tluoughout tif. ,o that rhey can co'linug to grow. Animals respond

to stimuli oftcn by movcnrcnt,largcly through lnusclc conuactions, in rcsponsc io nerves

so they can conLinue !o respou<l whcn grorvth has stoppcd'

Pages 19G-193

/? ts+cl The ansrver should includc some or all of rhc following. other poinri may be

valid

Part of plant

affected

Effect of red ti8ht(tight, build-up of Prq)

Effect of far red light(dark, buitd-up of P*)

seed stimulates germination inhibits germination

Stem elongation inhibited by red light elongation i5 stlmulated by far red tight

exposure to far ted llght gives the ssme

effect as etiolation

leaf expansion is stimutated by red tight

chlorophytt formation stimulated

expansion is inhibited by far red light

chlorophylt formation inhibited

lateral roots growth of laterat roots is inhibited growth of laterat roots is stimulated

flowering in SDP5 red tight inhibits flowering

in LDPs red light stimulates fiowering

in SDPs far red light promotes flowering

in LDPS far rBd light inhibitr flowering

Edcsccl A2 Uiology loplcmcnrarion md Asscssmenr cuidc forTcachcrs anriTcchniciins @Pci.son Eduouon Limiled 2009

,'t rqrnr r, rctr+Ul 1'he answers should include some or all of the fcvalid. ,__-s 'rlruqc surlc or ail oI rhe follorving. other points may be

Ed*ccl42 liology tnplemenurion od Asscssmcnr Cujdc forTilaclrcrs irndTLr :luicisns Ol>carson Educarion Limitcd 2009

IrE

t

iliT"rfi.f il;:,:._", messase is produbed in leaf exposed ro periods of light and

. If it is a chemical ,rto

the flowering.gpi-cgl l49ds-te m.

r1om 1. ",", * {',Ti: ;: H,H ::.l,,nffi :i,.;l ;,n:,#.";:Tj, -chemical to bc made arirJ movcd.

' Suggcsrs chemical messroo m^,,^. r-^_ - ,

both, message moves from onc plant to anolher ro stimulate florvering in

il,1'ffi:::n.uj",:fi:ll!; "'n' and dark

'IrrovLs (,ur i'ro risslics orhosr prant -

t :il:'

The answer should incrude some or at of rhe iolrorving. orJrer poinrs may be

Light detectecl by phy,tochrorncs in lcavcs + rhcn sshort-day pl.ntr. plit rlic llow chart lor long-day and

Shorr day: dark period ofappropriate length or farbalance "r or,r,".nr.*., ;J"^",:l"j:]:::*.:: ]T

red light- convcrsion of Ppa ro pp -, e a r c e,,s j &; il:,L:::, [ ,]' ill ]lT l' :; ;;:ffi",_..,a;;

* n o r'i o, ; g.,, i n

I ong day: dark period ofappropriate length or rcclbaiance .r phy,;.;;;;;; #"::::":jllt* ll"1."tht+. convcrsion or Pp ro pps -r e ar c eil s * 0

",u." ".":,il':: J:,: :;: j,Trff,l':, ; J,-,tr.r,"r_,.",1",; " 1

"i no, ie.n i "pages 194-195

1 Photopcriodism: involvcs a major physiological chanthe transfer of a message from rhe reaves ro *. o"r".lllilh.as flowering, which involves

been set up, it continuJs, d";;^" ::.,::^:l-" no*t"n.t regions of the plant; once ir has

Phototropisms: ,.,.,r.n -' depends'

9q p-!Yla!l1r9acp- and'florigcg'

source moves. ore localiscd; rely on auxinsl can easily be reversed rvhen light

j Because cocoa buttcr is a fat, only fat_soluble substanmessage passes tfuough agar (which is water-based) lces are able to pass tlLrough it.The

mcssagc must bc watcr-solublc. f,ut cannot pcnetate the fat, so the

, ,t1", The answer should include some or all of thevalid. ,-.q .*ruuq surne or a| of the follorving. Ottrer poiits may be

In all rhe experiments shown, the depencicnt variablc ,

;::,li:' ffi: l, ?:il:'o * * "' r' r'.

",,i p i oiililjil[ i]l'.'ffni"Ji..,, .

"r'om sho or ilil;; ;15'r1[::'j j;L, j]""' ti p in to a gar; D : substance dirrused

Delicate shoots so can eascapable of being repeat.otu{

ot damaged; simple design makcs invesdgations very clear;many dmes very cheaply and .asiry.

{$,f''iiti;r.l:

l.ffiiiii'r,r'rli:-ti:ii-',.'I !:'r .; a: i;

pages 196-197

1 [S+CI Unilateral light scems to causc the lAA molecules to move laterally across the

shoot, so that the side of a shoot exposcd to light contains less IAA than the side which

is not illuminated.This me ans that the shoot tip acts as a photoreceptor. More hormone

ditTuses dorvn to the region of ccli clong'.rdon on the dark side.The IAA molecules bind

to spccific rcccptor sitcs on thc ccll surfacc mcmbranes, acrivadng the acdve pumping

of hydrogen ions into thc cytoplasm,This changes ihe hydrogen ion conccnuation,

proviciing rhe optimum pFI for the cnzymcs tl'rat brcak bonds between adjacent ccliulose

microfibrils and keep thc wall flexible.The cslls absorb watcrby osmosis and the very

llexibic ccll rvalls strctch and allow tl-rc cclls t<t cxpand. livcntually, as thc ccils malure, the

1A-A is dcsuoycd by cnzymcs, the pH oirhc ccll tva'ils riscs and bonds form between thc

ceilulose microfibrils. So the sell rvall becomes more rigid and the ce1l cannot expand any

morc. Because rhere is morc IAA on thc dark side, tircrc is more cell elongation and so

grow,th on the dark side, resulring in the shoot bending tot'ards thc light. Once the shoot

is growing riirccdy towards rhc ligl-rt, rhc unilatcral srimulus is re movcd. The asymmeuic

transport ol IAA encis and thc shoot grou's suaight lowards *re light.

2 The answers should inciude somc or all of the follorving. other points may be valid.

a went's bioassay showed that the amount of gro*th (bending when the block was

placed asymmeuically) was direcdy related to thc amount of chcmical in the block.

This makcs it possible to s'ay that growth torv'lrds unilatcral light must be due to

higher levels of the chemical on the shaded sice rhan on rhe light side of the shoot.

b The current model of photouopisms cxplains the differcnce in elongarion of the cells

on rhc shady and light sidcs in tcrms of thc movcment of auxin from thc light to the

shady side, where auxin allows rhe ccll walls to rcmain flcxible for longcr.

Iidcxccl A2 Biology Inplcmcnradon ond Asrcssmcnt Guidc forTcachcrs andTcchiciaro OPeanon Education Limhcd 2009

ffi_

198-201Pages 198-201

1 Nervc fibre: axon of an individual ne rvc ccil; may carry impulscs to (scnsory) or from(moror) the brain but nor borh.

Nerve: bundle of nerve fibrcs, may bc alr scnsory, all motor or a combination of both.

2 [s+c] The answer should incrude somc or a[ of thc roliowinc. other points may bcv.rlid.

Ncrve ccll in cNS with dcndrircs ro synapsc rvirh and rcceive inpur fiom odrer nervecells, long axon/fibre to reach dssues, myelinared ro give rapid spced of impulseuansmission, synapses on effector to pass on impulsc.

3 In invertebrates, the speed of transmission of a nerve impurse is direcdy rerated rodiamerer of nerve flbre, and fiere is a limit to how big a nervc fibrc can grow Mosrvertebrate neurones are associatcd with Schrvann celld and thercforc hav-e a myelin sheathAs a result of the nodes of Ranvier, tle uansmission of a nervc impurse is much rasrer.so vertebrate nerves thar need to carry impurses fast are myerinared, with relativery smalrdiameters.Those that are not myerinarcd don't neerl lo carry impurscs very rast so theycan sdll havc small diamclcrs.

4 Squid giant axons are large as they carry impulses relarively quickly during anescape response.This means that they are easy ro find and. access and easy to insertmicropipenls into. squids are invertebrales, so thcrc arc arso f*vcr cthicar issues withusing.them in experiments of rhis type.

pages 202-205

1 The resting potential of a ncurone is produced by the differentiar exchange of ions acrossrhe cell membrane.The membrane is rclarively impcrmeabre to sodium ions, but quitefreely permeable to potassium ions. Thcre are arso very acdve sodium/potassium pumpswhich use ATP to move sodium ions our of rhe axon and potassium ions in- This lowers*re conccntradon of sodium ions inside the axon, because they are pumped_ out andcannot diffuse back in again. potassium ions are moved in to th. ..u by rhe'pumps butthey then diffuse out again arong a concentration giadient rfuough op.n potrsrio- ion.channels. Eventualry the rnovemcnr of posiriveiy charged potassium ions out of the celralong the concentration gradient is opposed by the elecrochemicar gradient. As a resurr,the insidc of thc cc[ is srightly negative rerarive ro the oursidc. This gives a potentialdifference across the membrane of around _70 mV.

Edcxcel 42 Biology Irnplcmcnution ud Assessmenr Guide forTerchers andTechnicians @pqrson Education Limircd 2009

: \::_ li. r:;i:;

;:{iiii:ii:iii;iill#,., ,..*"*,;""^,tJ:iJ;*.'i,i;".;ii*.;;J;*#*;;,;**=.*';i;*;l;*,i;".;rr*;*;l*r*

2 a An action potcntial is dre rcsult of a suddcn and dramatic incrcase in axon membranepermcability to sodiurn ions. Spicific sodium channels or sodiuin gates open up,' allorving sodium ions to diffuse rapidly into thc cell.'l'hc potential difference across

thc mcmbrane is briclly rcvcrscd, rvith the ccll bccoming positivc on the inside withrespcct. to the outside, at about +40 mV.'Ihis depolarisation lasts about 1 millisecond.

The sodium channels thcn close again and cxccss sodium ions are rapidly pumpedout by the sodium pump, using ATP ro supply cncrgy.ll:e permeability of thcmembrane to potassium ions is tcmporarily increased as voltage-dependent potassiumion channels open. Potassium ions diflusc out of the axon down their concentraliongradicnt and an elccuochemical gradicnt, aLuactcd by rhe negarive chargc on thcoutside of the membrare.The inside of the cell becomcs ncgative relarive ro the

outside once again, It takcs a lcw miliiscconds bcforc rhc resting potential is resrored

and the axon is re ady ro carry anorhcr impulse.

Thc rcfructory pcriod is thc rccovcry timc afrcr an acuon potential during which an

axon membrane cannot be resrimulated. It is the time taken for the sodium pumpand othcr ionic movements to restore the balance of positive and negarive ions tharproduce the resting porendai. Absolute rcfractory period is when the sodium channels

arc compictcly blockcd and no rcsting potcntial. As rccovcry progresses there is the

rclative refractory pcriod. Its importance is that it limits thc rate at which impulses

ravel along a ncrve fibrc, prcvcnting constant sucam ofimpulses, and preventing the

acrion potcnrial from r-ravclling backrvards along thc fibrc.

b An action potcntial cun bc rccordcd accuratcly by inscrting a very fine glass

microclecuode into an axon, Another electrode records the electrical potential fromthc outsidc. Thc results arc shorvn on an oscilloscope.

3 The graph shows that DNP prevents the pumping of sodium ions out of the axon.Thissuggests that the ATP is being used to powcr the sodium pump - when it runs out, thepump no Ionger works. As thc DNP is washcrl arvay rirc pumping of sodium ions outbegins again, suggesring that ATP production has started again.

4 [S+C] Theanswcrsirouldincludcsonlcorall olthciolloiving.Othcrpointsmaybevalid.

The rccording from thc wholc nervc shows an increasing lcvel ofresponse to an

incrcasing stimulus.This is bccausc morc and morc ncrvc cells within the nerve are

responding to dre stimuius.The responsc liom the single axon shows the typical all-or-nodring response - whcrc the responsc is thc same to u stimulus beyond a threshold levcl,

pages 206-209

1 The movcment ola ncrve impulsc along the fibre is the rcsult of local ion movementsborh in front of ancl behind the action potential. In an unmyelinaild o.ru. fibre rheseevents occur all along the membrane. Although each event takes only milliseconds, dtetime adds up as thc action potcnrial.uavcls along rhe fibrc.

In myelinatcd ncuroncs) ions can only pass in and out of the axon at the nocies ofIlanvicr,. So an action potcntial will junrp lionr onc nodc to dtc ncxt,This spccds up

' transmission as thc ionic movements occur much lcss frequendy taking less dnie.

Ederccl A2 Biology lmplemcnurion and Asscsm.nl Guidc forTc.chcrs andilcchniciens OPcrson Educarion Limited 2009

2 'fhey are involved in making the neuroransmirrer subsrances in rhe presynapdc knobs;involved in the producrion of vesicles; involved in the breakdorvn of neurotransmitters inthe synaptic clert; invo'lvcd in thc production of ATp !o powcr rhc various ion pumps andsynthesis and breakdown of neuroransmitters. Any othcr valid points,

3 [s+c] Theanswershouldincrudesomcorall orthefoilorving.orhcrpointsmaybevalid.

. Elecfon micrographs: show rhe presence ofvesicles in the synaptic knob oftheprcsynaptic neurone bcfore an action porcntial; aftcr rcpcatcd action potendals thesevesicles are no longer visible, implying that they have released thei. co.,tents as a resurtof stimulation' Also shows largc numbers or mitobhondria that suppry the energy for thesyn*resis of the neurouansmitrers cic.

Borulinus toxin: blocks the release of aceryrchoLine and so shorvs rhar acetylcholine fromthe presynaptic mcmbrane is needcd for thc transmission of an lcrion potential across asynap se.

Nicotine: sdmurares rhe nervous systcm by binding ro thc posr-synrptic mcmbranc,mimicking the effecr of aceryrcholine and so suggcsting that acerylcrroline does the same.Suychnine crc.: show thar acerylcholine causes the setting up of acrion potenrials inpostsynaptic neurones, because preventing the breakdorvn of acctylcholinc causes theneurones to respond continuously.

curare: shows that blocking of acctylcholinc srops .,ansmission of acrion potenriars fromnerve cells to muscle ceils confirming that acerylcholinc needs ro bir.rd to acerylcholinereceptors to initiate post_synaptic porential.

pages Zi0-21''l

I Accommodation occws whcn aLl of thc synaptic vcsiclcs in a synapdc knob aredischarged as a resuit ortoo many acdon potenrials in rapid succession.Therare ofsynthesis ofnew vesicres cannot keep up and the neurone can no longer respond to thestimulus, A short rest restores the response as new vcsicles arc madc. Accommodationallows organisms to ignore repeated harmless srimuli so rhat the cNS does nol becomeoverwhelrned with input.

2 spatial and temporal summadon make an orga;rism more responsive to smail stimurirvhich might not on their own trigger a response. A response coming into several sensoryreccptors at once, for example, can bc addcd togethcr to give arvareness, eg. the rodsof the eye. similarly, if a small srimulus rvhich,,vould nor rigger a post-syn;pdc acrionpotential on its orvn is repcatcd scvcrol timcs in quick succcssion, an organism becomesarvare of it, thus increasing scnsitivity and responsivcncss,

pages Z1Z-213

1 a !flhen a receptor cerl receives a stimulus, sodium ions move rapidiy across rhe' cell membrere sening up a gcnerator potcnrial- A small stirruius re sults in a smallgenerator poteir:;a! and a lrrgc stimulus rcsulL: i. a largc gcncrator porendal. ir rhegenerator potenrial is large enough to reach the threshord ofthc rcceptor neurone, anaction potential will result in Ihat neurone. Ifit is nor, rhere rvill be no acdon potential.

Edescel A2 Eiology lmplementrtion and Assessmcnt cuidc forTcrchers cnd rechnicians opcarson Educarion Limikd 2009

b ln convergence, even ifthe gencrator potential liom an individual receptor cell is

too small to set up an action potential, the gencrator potcntials from several may add

together or summale and uigger an action potential.This makes it possible for the

sensory system to rcspond to lorv-level stimuli.

2 [S+C] Theanswershouldincludesomcorall ofthe following.Othcrpointsmaybevalid.

. Accommodation: ovcrstimulation of any prcsynaplic ncuronc releases so many synapdc

vesicles that further action potentials in the neurone can't release neuroLransmitter

molecuies into the synaptic clcft and no action porendal is gcnerated in the postsynaptic

ncuronc.This mukcs it possihlc for thc auirnal to conccnl.ratc on ncw) and potcntially

motc important, stimuli. Rcsponse lcturns as new neuroLransmittcr is synthesised,

Adaptation: constant srimulation of rcccptor cclls rcsults in a gradual decline in response.

. Again this makes it possible for the animal to concent-rate on newi and potemially

more important, sdmuii. Animal rvill not respond again rcgardless of amounts of

ncurouansmittcr.

pages?14-217 I

1 a Rhodopsin is lorrncd lrom opsin and rctinal. In the dark, rctinal is all in the cis form.

Light converts this to Eans-retinal.This changcs the shape of the retinal, and the

rhodopsin breaks up into opsin and rctinal.

b The break-up of rhodopsin uiggcrs a cascade reaction that results in the closing ofthe sodium channels in rhe rod membrane, As the sodium pu:np continues to pump

Na* out of the cell, thc inrerior bccomes more negadve than usual.This produces a

generator potendal in the rod. Ifthe generator potential is iarge enough to reachthethreshold, or if several rods are stimulal€d at oncc, neurouansminer substances are

rclcased into the syn';psc rvith thc bipolar ccll.This scts up an aclion potential in the

bipoiar cell rvhich passcs rlcross the synapsc to cause an acdon potential in the sensory

neuronc lcading to thc brain. In thc visual areas of the brainthis visual iniormation is

convcrtcd into an awarcncss of thc imlgc.

2 a Sevcral rods synapsc rvith a single bipolar cell, so summation of generator potendals is

possiblc. In low light lcvcls which would not result in an action potential in the bipolar

cell from a single rod, summation of generator potentials from several iods can result

ir an action potential. Each conc synapses with a single bipolar cell so it is less likely to

uigger an action porcntial in dim light. In addition, iodopsin in cones needs to be hitwith more light energy than rhodopsin in rhc rods'bclorc it rvill break down. So, again,

thc rods rvill rcspond to dimmcr light,

b Severai rods synapse (convcrge) on a single bipoiar ccll.This means that subde

changes in light levcl as somcdring moves arc dctccted by rodl although notnecessarily clcarly. Cones nced much biggcr iight diffcrcnces, and there is no

convergence' so thcy arc lcss likely to respond to movement,

c Concs respond only to bright light, and each individual conc synapscs onto a singie

bipolar cell. As a rcsult any image is usually clear and crisp.

Edexel AZ Siology Implementltion and Asscssmcnr Guide forTcachers md'Ibchnicians @Pcanon Educarion Limited 2009

Pages 218-219

1 The need ro move the whole body around in animals means fasrer responses are required- electrical coordination makes this more possibic, chemicar coordinarion dcpends on'diifusionandmovementinmassflorvsystemssuchasbloodandphroemanisospeedislimited. It usuaily invoives grorvth as the mechanism of response. It is sufficienr for prantresponscs.

2 ts+cl rheanswershourdincrudcsomeorailof rhefoilorvirrg.orherpoinrsmaybevalid.

P[ants Anima[s

chemical coordination plant hormones (growth substances)control grow1h, movement, floweringexampies: auxins (lAA) gibbereitins, '

itorigen

retativety slow changes

animal hormones

controI growth, development, sexualmaturity, response !o stress, bloodsugar Ievels etc.examples: adrenallne, testosterone,oestrogen, human growth hormone,ins u lin

relatively slow changes

eLectrical coordinationnervous system composed ofconducting nerue celiscontrols rapid response to stimuli,e,g. reflexes, and brain allowscoordination of many nervous inputsailowing learning, habituation etc.includes chemicaI transmission atsynapses

can be very .apid, Long-term changesln synapses oi brain related tomemory

Light lalling on dre sensory celrs ofthe redna causes impulses to travel along neurbnesin the optic nerve to the brain.Thc impulses arc detccted in a conrror centre in themidbrain'The impulses travel arong neurones to further conrrol cen..es.These synapse

)l*.olun"nr,r of thc parasymparhcLic cranial ncrvc (rhc oculo'oror) which transmits

lmpurses to the iris.The impurses in the ocuromotor ncrve fibres srimulate the effectors(the muscles of the iris) causing Lrre circurar muscres to confact and the radial muscles to

;ffi *::::H:::, or action siorenriars rrom trr,", "" :-.,,;: ::"from the contol centres along sympathetic ngrves to the iris, the circular muscles relaxand the radial muscles contract and rviden the pupil.By reducing the amount of light entering rhe eye in bright condirions rhis reflex avoidsdamage to thc delicate rods and cones by overstimulatiig them. in dim right, the reflexcauses thc pupil to open wicle so as much lighr as possibie fails on the rods to maximisewllat you can see.

Pagesz2o-221

I 'l'he ccrcbral hcmisphcrcs arc associatcd with highcr brain functions - seqing, thinking,

learning and emotions for example. Folding of thc cercbral hemispheres increases the

surface area of thcsc rcgions of thc brain. It is thought that greater lolding and thus

grcatcr surf'rcc arca is associarcd with grcrre r intclligcncc, morc complcx emotions

and the ability to lcarn morc complix skills. Humans have grealer abiliries than other

primares, and morc folding.Thc volumc of tissuc is inrportan! too which is a function not

jusr of folding but of 'Iickncss. So dolphins havc big surfuce area but lcss volume because

rhe tissue layer is *Linncr. They are ve ry intciligenr but it is thought that their developmcnt

docs not rival humans.

2 tS+Cl The answcr should include some or all of the following. Other points may be valid.

Brain area Function

cerebral hemispheres vision, sight, thinking, learning, emottons

frontai lobe emotional responses, planning, reasoning. decision-making

primary motor cortex controts many movements

temporal lobe sound recognit!on, hearing, speech, many memory functions

occipital lobe vision, shape recognition, coiour vision, sense of perspective

cerebelium coordinates smooth movements, maintains posture and batance

hypothatamu5 coordinates autonomic nervous 5y5tem, inctuding thermoregulation, and

controls many basic drives, e.g. thirst, hunger, aBgres5ion, reProductive

behaviour

medutta oblongata controts reflex centres for heart rate, breathing rate, blood pressure, coughinS,

sneezing,swallowing, saliva production, peristatsis

Pages zzz-227

1 X-rays: pass *Lrough botiy, absorbcrl diflcrcnri'.rlly by diliirent tissues, make an image on

phorographic.f,lm. Good for taking images of hard tissuc, c.g. bones, but much less useful

for producing imagcs olsolt tissucs such as thc blain.

Computeriscd romography (C'f scan): thousands of tiny bcams of X-rays passed

*rrough an arca of rhc body, c.g. hcad. Bcams attcnuatcd by fie density of the tissue .

The X-rays which makc it through arc detccted and mcasurcd. A computer collates the

data ro produce a cross-scctional image ofa thin siicc tluough rhe body. Special dyes can

makc areas X-ray opaquc so they show up more clearly in the scan. Can identify major

suucrures in rhe brain and dctcct problcms such as brain tumours, blecding in the brain

or swellings of thc artcrics in the brain (ancurisms). Cannot be used to show how areas

of the brain are used or change during diffcrenr acdvides. Can be linked to observed

changes in behaviour to indicate rhe importance of certain areas ofihe brain in particular

functions,

Magnctic rcsonancc imaging (MI{l scun): Uscs magncric licltls and r0di0 waves to image

the sofi tissues (mainly due to amoun! of watcr in tissue), so no potendally damaging

X-rays. Particularly good for imaging watcr in the body.The signals are analysed by

computer and used to producc an image. Images show much finer detail than CT scans.

Edcxccl A? Diology lnplcmcntation und Asscssmcnt Cuidc for'lilrchcrs rndTcchnicius OPurson Educrtion Linritcd 2009

2D scans are usually produccrl - a computcr can creatc a 3D image fiom these. Candistinguish regions of the' brain. widely used to diagnosc brain injuries, strokes) rumoursand inlections of the brain or the spine. Can also indicate links benvcen the srucrures inthe brain and patterns ofbehaviour.

Functionar magnetic resonance imaging ('MRI):monirors uprakc of oxygen in dirferentbrain areas, so indicates active areas ofthe brain. can be obscrvco ;n r.riti-a, so makesit possibre to watch brain response while pcople carry ouqtasks. Gives an exrremerysparialiy accurate image of the brain. Has to bc carried out rvirh parient,s head remaining

' complctcly still, which limits tasks that can bc clonc. uscd meinli ro investigate normalbrain structure and function. May soon be used to diagnosc diseases such as the earlvsigns ol suoke damage aod rhe onser of Aizheimers.

2 [s+c] The ansrver should inciude some or ail of rhe foilorving. orher points may bevalid.

Absolutist: Animals should not be uscd for cxperimenrs - in rhis case for learning moreabout horv the human brain might rvork. r\,roraily, experimendng on animals tha! causespain or death is completely unacccplable,

Relativist: It is morally more acceptable to cxpcriment on an.imals as a model lor humansrvhere there is a posirive purpose ro the rcsearch, e .g, it will benefit rhe ueatrnent ofirumans with disease or damage to the brain.

pages 22&_231

1 [s+c] Theanswcrshouldincludcsomcorrll ofr]refollorving.orherpointsmaybevalid.a Absolutist: it is completely unacceptable to experiment on animals causing pain or death.

Relativist: the work of crowley and Kau could not cthically havc been carried out onhumans, but ir rvas important research that helps us understand the deveropment ofvision in mainmals, incluaing humans and drcrcfore jusriticd uring pri,.',"r.

b Absolutisu it is completely unacceptable to experiment on animals causing pain or death.Relarivist: the work of veisel and Ilubcl could nor ethically have been carried our onhumans, but it was important research that helps us understand the development ofrision in mammals, including humans. It rvould not be erhical ro use primates lor thiswork as it was not direcdy of mcdical benefit, but kinens are more readily availableexperimental animals and therefore it is acceptablc to usc thenr.

ts+ cl 2 ' Animal rvork with embryos examining the srrucrure ol *,. brrin as it is.laid downto show rhat the basic stucturc dcvelops at a specific stage offcrar developmentregardless of inpur.

' Animar rvork with kittcns sdtching eycs srrut at various stagcs of developmcnt toshow rhat there is a criticar window during which ross of sight becomes permanenr,suggesting that dris is when the mature visual cortcx devclops.

. Animalrvorkwirhmonlcvsshorvingsamethingas\\.or, \viLhkinens_different

cntrcal pcl lod.

' Human obscrvations, made on babies who are blind for some rcason during thecritical window, e.g. babies who nceded surgery on cataracts etc.

Edcxccl A2 Biologv Implemenratioo and Assessmcnr Guide forTeachcrs aDdrcchnicirns opcarson Education Limircd 2oo9

..i:"::

.:; ?,

.t, ilt:lrx

Answcrs should show aw{rrcncss rhat it is unethical to cxperiment on human infants inthc rvay rvork has bccn donc on kittcns and monke.vs, and that evidence might come fromcircumstances rvhere babics are born with damage to brain areas or who are temporarilyblindcd/cicprivcd of sight for sonrc rcason.

They wcre the fust people to shorv that rhe brain is very plastic; rhat at birth, although

many ofthc ncural arcas arc prcscnt) thcy nccd input and cxpcricnce to develop and workfully.They dcveloped the idca and produced evidcnce to supportthe concept ofcriticalrvindorvs of development rvhich underpins much of our subsequent understanding ofhow the brain works.

gages 23?-237

1 The period ol time during rvhich vital neural connections are made in the brain inrcsponse to specific stimuli.

Nature: axons from the lighr sensidve cells in the retina grow synapsb in visual cortex in

a very regular way known as ocular dominance columns. Neighbouring columns of cells

receive input from the same area of the redna from the left eye and the right eye.

' Nurturc: right srimulation nccdcd during cridJal windorv ol dcvelopment for the area

of the brain to develop propcrly. If rhe nccessary input during the critical period ofdcvelopmcnt fai1s, thc opportunity to makc thc viLal ncural conncction can be lost

permanendY.

2 [S+C] The answer should includc some or all of the foilorving. Other poinrs may be valid.

Must consider the necds of the baby first and thc needs of research less important,c.g. ir would be erhically unacccptabic ro lcave a ncrvborn baby with cataracts in order to

test a hypothesis whcn it is known that the cataracts rviil inicrlere with the development

of vision as the baby grows up. As long as the baby is not harmed or deprived in any way,

Ihcn research could bc acccptablc.

J JO

b20c Each time a crirical window of dcvclopmcnt appcars, new neurones and conncctions

arc laid down if the appropriatc stimulus is prcsent.This incrcases the size of the

brain. lf the child is dcprived of the stimulus, the brain does not develcip fully, and

once the cridcal window has passed, that damage cannot be undone so lhe brain ends

up smaller. In childrcn who suffer severe neglect, many critical windows are missed

and so brain dcvclopmcn! is scvcrcly alfcctcd.

4 tS+C] The answer shouid include some or all of the following. Othcr points may be valid.

Damagcd brains: shorv rvhat happcns to thc pcrson as a rcsult ofepecific damage or

disease; may be difficuit to separate the effect on specific areas of the brain if more than

one rcgion damagcd;somc kinds of damage are vcry rarc, so takes a long time to collect

sufficient cvidcncc ol its cffcct.

Newborn babies: looks at horv newborn babies respond to different stimuli; very limitedin what can be donc as cannot harm thc babies; useiui because the effect ofnurrure is

minimal at this stage, so c:rsier to separate from the efici:is of nature.

Erlcrccl A! lliology Inrplcmentation rnd Asscssmcnr Guidc for'lirclrcrs and l'ccluricians Ol'crrson l-ducction Limitcd 2009

Twin studies and face recognition: comparison olresponses from lraternal and iclenticaltw'ins; should hclp to separatc our rhc cllccts of r]'c cn*ironmcnr and the genes. Howc'cr,rhis assumes thar idenrical rwins develop identically from their genes, and this may not beuue in all cases.

Cross-cnltural studics: looks at thc impacr of dillcrcnt bclicls and mcthocls on behaviour;. can be used to look at distinct differences in nurrurc. IJowevcr, cvery individual is

different and not everyone is alfected by rheir culrure ro dre same extent.The level ofthese differences benveen individuals may be difficult ro.measurer and so dilficult tocorrelate rvith the resulls from the study.

pages 238-239

1 lnnate behaviour shows there are genetically determined responses to certain srimuli*'I.ricl: occur as a rcsuk of specilic ncrvc pathrvays laid dorvn in the embryo from theinstructions of the DNA.The stimulus for a piece of innate bchaviour will always elicitthe same response and thc development of thcse neural pathrvays in the brain dependsalmost enrirely on the informadon in the DNA.

2 Animal behaviour can be used ro see the importance of nature on brain developmentthrough the srudy of innate behaviour ancl the role it plays in animals of dillcrenr species.Lcarning behaviour lrom habiruation and condirioncd reficxcs ro exploratory and insightlearning all play an important role in deveroping understanding of nurrure in braindevelopment.'Vhich behaviours are completely the result of gcnetic pathways and whichdepend on learning (nurrure) as well. For example, marernal behaviour might be thoughtto be instincrive and some aspects arc, but animals rvhich arc hand-rcared with no conractrvi*r rheir own species are.often incompetcnr mothers. Any othcr valid points

pages 240-2411 Invertebrates with fast irnpulses in unmyelir.rared nerves have rclarively largc diameter

nerve fibres rvhich make the {lbres rclatively easy ro idcntily and sdmulare artificially.Also, as invertebrales, less ethical issues arise from their use as experimental animals,

2 [s+c] The answer should include some or all of rhe following. orher points may bevaIid.

Habituarion and accommodation both lead to the reducrion in rcsponse to permanentor rapidly repeated srimulus. Accommodarion is rhe physicar rcsurt of dcpretion ofncuroiransmirrer and synapric vcsiclcs in drc synapric knob ofa prcsynapdc neurone.After a brief absence of rhe stimulus (action porendal in r-he prcsl,nxptic ncuronc), theneurotransmifter and vesiclcs arc resynthcsiscd rnd rlrc rcsponsc rcsrorccl. Habituation isthe result of.loss of response of tl-re calcium ion channels in rhe presl.naptic membrane,resulting in a ioss ofrcsponse to an aclion polential in the ncuronc. It is a rearningresponse' and can be retained over a long time, reducing the response to things thathappen constan'jy or very frequendy and so lcaving thc brain betrcr able ro focus onoccasionally changing s'-rmuri which may be more impr.:tant for survivar.

Edexcel A2 Biology Idplemenution rnd Assessment Guide fortachers !od'rcchnici. ns Ope3rson Educadon Limitcd 2009

Pales 242-247

I Ncurotransmittcr synthcsis and storagc: If a drug blocks lhis proccss, s5'naptic

trrnsnrission *'ould lcsscn ancl thcn stop rs supplics oI ncurotransmitter rcduced. Thisrvould mcan nerves using drat ncurotransmittcr rvould no longerbe able to pass impulscs

bctwee n thcm, causing loss of motor or scnsory skills and processcs in the brain.

NeuroEansmitter telcasc: A drug stopping ncurotransmittcr rclcase tvpuld st-op synapilc

ransmission as the impulse in the presynapuc llbrc would notbe uansmitted to the post-

synapric membrane causing ioss of motor or sensory skills and p.ocesses in the brain.

Neurotransmitter-receptor binding: A drug blocking this rvould slop lhe development of

rhc posr-synaptic potcndrls rvhich in rurtr would prcvcnt tlIc development of an acdon

potcntial in thc post-synaptic 6brc. Alrcrnativcly the drug may maintain binding so thar

rhe stimulus to the posr-synaptic fibre was conLinuous, causing confusion and farigue

lurthcr in lhe system.

Ncurouansmirtcr rcuptakc: a cirug blocking this rvouid slorvly rcducc tl-rc iutcnsity of tirc

rcsponse as less neurotransmiticr rvould bc resynthcsiscd and be ready for rclease.This

rvotrlri slrccd rtp fnrillrtc ctc.

Neuroransmittcr brcakdown: a drug blocking *ris rvould mean that sdmularion would

continue as the concenlr4tion of neurotransmitLer in tJrc synaptic gap rvould build up

steadily so therc rvould be consLant stimulaLion of tl-rc post-synapLic mcmbrane and

latiguc.

Z Dopaminc synapscs: produce tltc neurolransmitter dopanrine, the axons from them

spread tlrough the fronral corrcx, rhc brain stcrn and thc spinal cord, so thcy are closcly

involved in the conuol and coordinarion of movcment.

Scrotorlilt synupscs: pLorluec scr'otolrin in t groLrp of cclls in rl:c brain sicm rvith axtlns

that spread throughout the brain inro thc coltcx, thc cerebellum and the spinal cord.They

have a rvidespread influcncc on cclls throughout thc brain so low levels mean overail brain

acdviry is supprcsscd. Particularly reiatcd to diprcssion.

L-dopa EcstasY

precursor of dopamine so crosses the btood*brain

barrier

crosses blood-brain banier

enables brain cetls to maximise dopamine

production

affects serotonin synapses in brain, blocks the

serotonin reuptake system so synapses flooded

with serotonin, and may cause retease of alt the

serotonin from presynaptic knob. ilooding br:in

with serotonin

relieves stiffness and slowness of movement acts as stimuLant to brain and ptychotropic

therapeutic improves mood, sense of well-being, energy etc.

physiological effects include increased heart

rate, change in thermoregutation, loss of thirstsensation, orevention of urine production by

kidney

lidcxccl A2 llioloijy Ln il"mcntu'ioo rnrl Ai*cssmcnl Cuidc for -l r-;hcrs rod'icchnicirns 4)Pcrrsnn Ilducrric;. 1 .:nilcd 2009

4 [S+C]valid.

sSRIs seem to work by blocking the serotonin reuptake proteins and so maintain arelatively high level ofserotonin in thc synaptic clefr, to bind wirh the post-synapdcmembrane receptors. Horvever the working hypothesis from the genetic evidence is theopposite.The short form ofthe seroronin reuptake protein allere and its frequency (i.e.in homozygous or hetcrozygous state) afrcct rvhether or not lhc person is likely to sufferfrom depression. People with the short form produce less ofthc reuptake protein soserotonin is taken up more slowly by the presinapric neurone aficr its rerease into thesynapse. Logically this rvould rcsult in riore scroronin bcing left in rhe synapric clefr ancisc less depression - in the same wa]- as oeopre respond ro SSRIs. ln realiw, peopre rvirhdte short form are more likely to expcriercc c.lcprcssion. Pcrhaps rhcy have lcss scroroninavailable in the presynapdc knob to be rclcascd rvirh *rc subscqucnr impulses? Furri:rerinvestigarions rvould need to look at horv much serotonin is in the prcsynapric knob, and/or horv much and how Iong seroronin remains in rhe synapric clc[r in rhe diffcrent genericiorms and during trcatment with SSRIs.

pages Z4B-25'l

1 The Human Genome project has idenrified alr or the human gcnes and incrcasinglyidentifies the genes thar are associated rvith particular diseases and risk g.o'pr.Tii, i, th"information on which pharmacogcnomics builds as ii dcvclops medicincs *rat ivork wirha pardcular genome,

2 The abiliry to prescribe fic right drug for an individual padenr rhrr rvould work with theirparricular genetic makeup. It wourd increase the abiliry to prcscribc the right and rowestpossible dosage with minimal risk ofside effccts or adverse drug reacdons.

3 [s + c] The ansrver should incrudc somc or all of thc folrorving. orhcr poinrs may bevalid.

Itlentificadon of genes for trcarment: Lime-consuming and expcnsivc; rcsponse to drugscan be complex; should the moncy be invcsred in this kind of rcscarch that will benefitjust groups of people, or wourd it be betrcr to spcnd it on somcdring ,h", b.;;;;-cvcryonc?

cost: having idcntified rhat only l proportion of a popuration u,il bcncfit, is it socialryand morally acceptable to produce a drug that works for thcm, br,rt not one that *,orks lorothers in that population) rKnorving your genes: shourd only you knorv, or should genomes be stored for anarvsisby drug companies ro herp rhcm dccidc whar drugs rJrcy shouid lbcus on? shouldindividuals bc told about gene vrriants rh'.rt mry lead to other problems *rat can,t betackled, or is it bctter nor to know?

Cost of training: to keep doctors and pharmacists up to date; rvill cost sociefy but wouldbe essential.

Edercet A2 Biotogy lmplementauon and Arsessmcnr cuidc for'lccchcrs anJ'lechnicirns Gll,carson Education Limired 200i1

1',i::.';,j-;:1'.1 r;,:;i *:,1 - :'..;: ._':, ir :'r' : .. :r ... .1. :

t{-its!.a!(4r-4*1it\St

[S+C] 1'he ansrver shouid include some or all of the follorving. Other points may be .

valid.

Nlany possibilities including: kappa-opioids as painkillers lor women; screening forcytochromc P450 bcforc drug trials; idcntifying 'at risk' ir.rdividuals for certain rypes of cmcer

to allorv reatment belore lhe canccr starts; P-glycoprotein transporter substance affects the

ability of pcople to takc up digoxin, a hcart drug - onc gcnotypc rcsults in a far grcatcr uptake

of dre drug than anotherl racial variador-rs, e.g. incidcnce of hcarr disease in Asian populadons

and dcvelopment of drugs targctted at peoplc with a spccrlic genetic profile.

Pages 252-257

1 The diagram given herc is a minimum. Givc crcdit for any correct extra details

[S+C] The answer should include some or ail of thc following. Other points may be valid.

(i) Wrong to use gcnclically enginccred organisms under any circumstances,

(2) Thc potcntiai bcncfits ol thc use of gcnetically cngincered microorganisms far

ounveigh any risks.

3aDrugs from GM plant Drugs from CM microorganism

required gene cut from human or other

organism and inserted into Ti plasmid ofAg rc b act e t i u m tu m ef ac i e n s

required gene cut from human or otherorganism and inserted into plasmid

plant cells infected by modified A. tumelacienswhich transfers desired gene to the ptant

genome

plasmid transferred into host bacterial cells

v/here it becomes part cf bacterial DNA, marker

gene usually added

plant cells then cloned on suitable hormone-

containing medium to produced mass ofundifferentiated modified plant cells

bacteria identified by marker cultured in

fermenters to make new protein drugs

piant celts then transferred to suitabie mediumto produce huge numbers of CM planttets thatwill mature to produce the desired drug in theitleaves/[ruit etc.

downstream processing required to separate the

microorganisms and the desired end-product

ffi

gene insertedusing DNA

iigase

niodificd bactcriummakes drug as new

gene expressed

42 Biology lmplementato! and Assosmenr Guidc forTecchcrs add Techoiciins 9Petuson Education Linitql 2009

,r;:l.il,:l.i::,,i:::i1l

riii;ii

b Risks: cost of developmcnt may crctcr companics ancr mai'use in less-deveiopedcountries, possibiliry that GM crops rvill inrerbreed with rviid species and changethem, or rhat Glr,l planrc rvill lose thcir abiliry to produce drc vaccine.Benefits: long-rerm, reladvery cheap, can be grown by communiries that need themaround the rvorrd, no problems lvith needing cool storage or speciarised medicalpcrsonnel to deliver, easy for children or adults to takc.

IS+c] -l'heanswershouldincludesomeoralrofthefoilorving.or},erpointsmaybe

valid.

Possible examples include : blood-clouing ftctors F:rcror VIIrabbit milk; alpha-1-antiuypsin from shccp milk; ATryn (foranrithrombin dcficicncy) lrom goat milk.

Evaluadon will depend on drug chosen, but should includc an assessment of costtlf producing the drug, cflcct on animals usccJ, strcccss ol'prpgcclrrrc uscd to crcrrcua'sgcnic animals, benelis to people rvho are rreated wirh the drug compared rvithprevious feauTrcnr.

IS+c] Theansrvershourdincrudesomeorall ofthcfoiloiving.oLherpointsmaybevalid.

Ansrver nceds to includc poi.ts such as gcncricaily *ociirictl microorganisms, plantvaccines, GM crops etc.

Benefits inciude:

' specific drugs ma<ie in large quantiries in conuolled rvay. lose depcndencc of chcmicals cxuactcd lrom animal cadavers

' drugs/vaccines produced in a way rvhich makes delivery/cosr ctc. in de'eloping worrdeasier

' plants modified to suir growing condirions/nutritional rcquircmcnrs erc.Risks inciude:

' risk of relcasc into outsidc worlLi

' risk of conramination of natural plants lvi*r gene markers, c.g. inferillity' cost to countrics which cannot arford the GM technology for drug or foods.

Edexcel A2 Biology Implemcntatioo and Asscssmcnr Guide forTclchcrs and rcchnicians opearson Educarioo Limited 2009

and IX lrom goar/sheep/' trcrring l'rcrcditary