An investigation was carried out into the effect of light intensity on the uptake and release of carbon dioxide by two green plant species J and K.

Single leaves of each species, still attached to plants, were sealed in glass vessels containing a known mass of carbon dioxide. The leaves in the vessels were exposed to light of known intensity for one hour. The change in mass of carbon dioxide in each vessel was determined and the change in mass of carbon dioxide per cm2 of leaf surface was then calculated. The experiment was repeated at a range of light intensities for both species.

The results are shown in the graph below. Light intensity is expressed as a percentage of normal daylight.

+ 2 0

+ 1 0

0

– 1 0

– 2 0

– 3 0

– 4 0

– 5 0

– 6 0

– 7 0

L ig h t in ten s ity% n o rm a l d ay lig h t

Cha

nge

in C

O i

n 1

hr/

g cm

2

–2

S p ec ie s J

S p ec ie s K

5 1 0 1 5 2 0 2 5 3 0 3 5 4 0 4 5 5 0 5 5 6 0

Adapted from Plant Physiology, Salisbury and Ross (1978)

(a) (i) From the graph, determine the light intensity at which there is no net exchange of carbon dioxide by leaves of species J and K.J 2.5 – 3.0%;

K 6%;

(2 marks)

(ii) Comment on the relationship between light intensity and the exchange of carbon dioxide in species J.CO2 decreases / OR uptake increases as light increases;gradient steepest up to 5%;little change after 15% / eq;(nett) CO2 produced / OR released up to 2.5/3% / below 3.0% / converse;correct ref to relative rate of photosynthesis and respiration;correct ref to compensation point;

(3 marks)

(b) (i) Give two differences between the curves for species J and K.Any 2 points allowed.

gradient steeper / eq;

levels off (at lower light intensity) / reaches a maximum;

maximum rate of uptake is lower / eq / OR 33 units difference / higher uptake in K at high light intensities;

change not directly proportional to light intensity;

J has a higher uptake below 19.5%;

J reaches its compensation point at lower light intensities than K;

Allow converse if K stated.

(2 marks)

(ii) Suggest which species would be better adapted to a shaded habitat giving a reason to support your answer.J;

compensation point / eq at lower light intensity / faster rate of photosynthesis at low light intensity;

If K given, only allow if state that in the shade, light intensity is likely to be 20.5 – 55% of normal daylight; [So 2 or O!]

(2 marks)

(c) (i) State one environmental factor, other than light intensity, which could also affect the uptake and release of carbon dioxide in the two plant species.temperature / light quality / wavelength / water availability / wind / air speed / oxygen;

(1 marks)

(ii) Explain why the factor you have chosen in (i) has an effect on carbon dioxide uptake and release.temp: affects (rate of) enzyme reactions;

Calvin cycle / light independent reactions uses CO2 / OR respiration releases it / OR ref to photorespiration at high temps.

light quality/wavelength: pigments absorb specific wavelengths / eq;

rate of photosynthesis changes so CO2 used - uptake changes;

water: plant wilts / stomata close / converse;less photosynthesis so less CO2 used / CO2 cannot enter / converse;

wind / air speed: increased water loss so stomata close;less photosynthesis so less CO2 used /CO2 cannot enter / converse;

oxygen: reduces CO2 uptake / increases CO2 release;competitive inhibitor for RUBISCO / OR combines with RUBISCO / OR ref to photorespiration;

(2 marks)[Total 12 marks]

The statements in the table refer to the light-dependent and light-independent (dark) reactions of photosynthesis.

If the statement is correct for the process, place a tick () in the appropriate box and if it is incorrect, place a cross (x) in the appropriate box.

S ta tem en t

O x y g en p ro d u ced

C arb o n d io x id e fix ed

O ccu rs in s tro m a

U ses N A D P H an d H

L ig h t– d ep en d en treac tio n

L ig h t– in d ep en d en treac tio n

;

;

;

;

;P ro d u ces AT P

[Total 5 marks

The diagram below shows some of the processes which occur in the light-independent reaction of photosynthesis.

5 ca rb o n co m p o u n d + X

Trio se p h o sp h a te

G lu co se p h o sp h a te

YN A D P H + H AT P

+R eg en e ra tio n

(a) Name the substances represented by the letters X and Y.X carbon dioxide / CO2;

Y PGA / phosphoglyceric acid / eq;

(2 marks)

(b) State the origin of the NADPH + H+ and the ATP used in the light-independent reaction.

the light (dependent) reaction / stage (of photosynthesis) / grana / thylakoid / non-cyclic photophosphorylation;

(1 marks)

(c) Where in the chloroplast does the light-independent reaction occur?stroma (of chloroplast);

(1 marks)

An experiment was carried out to investigate the effect of light intensity on the rate of photosynthesis of an aquatic plant, using the apparatus shown in the diagram below.

L am p

B u b b lesco lle c t

F la re d en do f ca p illa rytu b in g

P la s ticc on n e c tion

P o n d w e ed , cu ta t up p e r e n d

S ca le

C a pilla ry tu b in g

W ater

S y rin g e P las tic c o nn e c tio n

(a) State two environmental conditions, other than light intensity, which would need to be controlled. For each condition, describe how control could be achieved.

Condition 1 & 2

How controlled carbon dioxide 2 pairs as, condition; how controlled;

temperature; use of a water bath

carbon dioxide; use of (hydrogen) carbonate;

wavelength; use of same lamp/filter;

pH; use of a buffer;

(4 marks)

(b) The plant was allowed to carry out photosynthesis for 10 minutes. Describe how you would use the apparatus to determine the volume of oxygen produced by the plant during this 10 minute period.

switch off lamp/eq;

use syringe to move oxygen/gas bubble to the scale;

measure length of bubble on the scale;

multiply by cross sectional area of tube/ ref to calibration of the tube as a volume;

(4 marks)

(c) Using this apparatus, the volume of oxygen produced after 10 minute periods of photosynthesis was determined at different light intensities. The results of this investigation are shown in the graph below.

Vo lu m e o fox y g e n / m m

2 .5

2 .0

1 .5

1 .010 0 0 20 0 0 30 0 0

3

L ig h t in ten s ity / lux

The graph below shows how the wavelength of light affects the rate of photosynthesis.

xx

x

xx

xx

xx

xx

x

x

4 0 0 4 5 0 5 0 0 5 5 0 60 0 6 5 0 7 0 0 7 5 0

1 0

8

6

4

2

0

R ate o fp h o to sy n th es is/ a rb itra ry u nits

W a ve len g th o f lig h t / n m

(a) (i) What name is given to the relationship between wavelength of light and the rate of photosynthesis, as shown by this graph?action spectrum;

(1 mark)

(ii) From the graph, state the optimum wavelength of light for photosynthesis.450 nm;

(1 mark)

(iii) Explain the effect on the rate of photosynthesis of varying the wavelength of light from 550 to 700 mm.625 gives max rate / rate fluctuates / steep fall after675; reference to secondary pigments;

different pigments absorb different wavelengths / eq.;

chlorophyll a peak absorption 600 – 650;

chlorophyll a peak absorption at 650 – 675;

pigments do not absorb wavelengths above 675;

(2 marks)

(b) (i) Name the stage of photosynthesis the produces oxygen.light dependent stage / eq.;

(1 mark)

(ii) State where in a chloroplast this stage would occur.grana / thylakoids;

(1 mark)[Total 6 marks]

The diagram below is a summary of the light–dependent reaction of photosynthesis.

L ig h t– d ep en d e ntre ac tio n

L ig h t en erg y +

w ater

N A D P H + H

C o m p ou n d X

G as Y

+

(a) (i) Name compound X.

...………………………………………………………………………………(1)

(ii) Name gas Y and describe how it is produced.

...………………………………………………………………………………

...………………………………………………………………………………

...………………………………………………………………………………

...………………………………………………………………………………(3)

(iii) State where in a chloroplast the light–dependent reaction takes place.

...………………………………………………………………………………(1)

(b) Name one pigment which is responsible for the capture of light energy during light–dependent reaction of photosynthesis.

...…………………………………………………………………………………....(1)

(Total 6 marks)

(a) (i) ATP / Adenosine Triphosphate [not Adenine] 1

(ii) oxygen 1photolysis / splitting / breaking up of water[not photophosphorylation] 1from hydroxide (radicals) /OR equivalent from equation 1electrons donated/eq to photosystem / primary pigments 1

max 3

(iii) grana / granum (lamellae) / thylakoids 1

(b) chlorophyll a / chlorophyll b / carotene / xanthophyll / fucoxanthin[not chlorophyll / PS680 / PS700] 1

[6]

The diagram below is a summary of the processes that take place during the light-independent stage of photosynthesis in a palisade cell.

C o m p o u n d P + C O 2 2 × C o m p o u n d Q

+ AT P+ C o m p ou n d R

O th er sug a rs 2 × G ly c era ld e h y de 3 – p h o sp h a te(T rio se p h o sp h a te )

(a) Name compounds P and Q and R.

P. ................................................................................................................................

Q. ...............................................................................................................................

R. ................................................................................................................................(3)

(b) Some of the glyceraldehyde 3-phosphate produced is recycled to form compound P as shown. What name is given to this whole cycle?

.....................................................................................................................................(1)

(c) Some of the sugars produced are stored temporarily within the palisade cell. Name the form in which they are stored and state precisely where this store is located within the cell.

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(Total 6 marks)

Photosynthesis is a complex metabolic process which can be influenced by many different environmental factors.

(a) Explain the term limiting factor with reference to photosynthesis.

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(b) An investigation into the effect of light intensity and carbon dioxide concentration on photosynthesis was carried out using pond weed. The pond weed was placed in a test tube that contained pond water and a quantity of sodium hydrogencarbonate. The light was provided by a lamp. The oxygen bubbles produced by the pond weed were directed into a length of capillary tubing.

The graph below shows how the rate of oxygen production of the pond weed changed with light intensity when immersed in two different concentrations of sodium hydrogencarbonate.

0 .8

0 .7

0 .6

0 .5

0 .4

0 .3

0 .2

0 .1

00 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 3 5 0 4 0 0

L ig h t in ten s ity / a rb itra ry u n its

R ate o f ox y g e np ro du c tio n/ cm m in3 – 1

– 3

– 3

0 .5 m o l d m sod iu mh y dro g en ca rb o n a te

0 .1 m o l d m sod iu mh y dro g en ca rb o n a te

(i) Explain the shape of the graph between a light intensity of 0 and 400 arbitrary units in the sodium hydrogencarbonate concentration of 0.5 mol dm–3.

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(ii) Describe and explain the effect of increasing the concentration of sodium hydrogencarbonate, on the rate of oxygen production.

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……………………………………………….…………………………..……(3)

(iii) A number of precautions would need to be taken while carrying out this investigation in order to obtain reliable data. Describe one precaution and explain why this precaution is necessary.

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……………………………………………….…………………………..……(2)

(c) During the light-dependent stage of photosynthesis, oxygen is produced by photolysis. Describe the process of photolysis and explain its role.

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……………………………………………….………………………………………(3)

(Total 14 marks)

(a) It is a factor which limits the rate (of photosynthesis / of a reaction) ;Increasing this factor increases the rate (of photosynthesis) ;Until another factor limits the rate / eq ; 2

(b) (i) 1. Increase in rate from 0 to 300 / 350 (light intensity) ;2. Reference to manipulated figures to support increase ;3. Light is the limiting factor / eq ; [accept converse]4. Rate levels off / eq above 300 / 350 (light intensity) ;5. Another factor has become limiting ;6. Named limiting factor: carbon dioxide / temperature /

chloroplasts / chlorophyll ; 4

(ii) 1. (Provides) carbon dioxide ;2. Rate of, O2 production / photosynthesis, is greater

(at all light intensities)above 50 for higher carbonate / CO2 concentration / eq ;

3. Reference to comparative figures for rates / approx. double ;4. For both concentrations rate starts to levels off at 300 /

350 light intensity / lower concentration levels off above250 compared with 300 ;

5. Hydrogen carbonate / CO2 concentration is a limiting factor / notlimiting up to light intensity 50 ; 3

(iii) Keep temperature constant / place tube containing pond weed in a waterbath ;Reference to rate of reaction / enzymes being affected by temperaturechanges / temperature affects, solubility / diffusion / volume of oxygen /kinetic energy ;Repeat / replicate ;To avoid anomalous / eq results ;Use the same piece / length of pond weed throughout ;A different piece could have, more / fewer, leaves / different surface area / eq(and so affect the volume of oxygen produced) ;Reference to equilibration / eq ;To make sure pond weed is acclimatised to new conditions ;No air bubbles in equipment ;So measuring only gas / oxygen given off ;Same type of light source ;So keep wave length the same ;No external light sources ;To control the experimental light intensities ; 1+1

(c) 1. Splitting water in (presence of) light ;2. H2O ½ O2 + 2e- + 2H+ ; [allow words]3. Electrons replace the electrons lost from PS11 / P680 / chlorophyll ;4. Hydrogen ions picked up by NADP / hydrogen ions reduce NADP ;5. NADPH / eq used, in light-independent reaction / Calvin cycle / to

reduce carbon dioxide ; 3[14]

The graph below shows the absorption spectra for three photosynthetic pigments found in a leaf.

C h lo ro p h y ll b

C h lo ro p hy ll a

C a ro ten o ids

A b so rp tio no f lig h t

4 00 5 0 0 6 0 0 7 0 0

Vio le t B lu e G reen Yello w O ran g e R edW av e le n g th / n m

(a) Describe the absorption spectrum of chlorophyll a.

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(b) Using the information in the graph, explain why it is advantageous for plants to have more than one type of photosynthetic pigment.

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(c) Describe a technique that you would use to separate the photosynthetic pigments found in chloroplasts.

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(Total 8 marks)

(a) Two {peaks / eq} at 425 - 440 and 665 - 675 nm ;

Little {absorption / eq} between 450 and {600 / 650} nm ;

Second peak {smaller / lower than first} / quoted difference / no absorption470 – 480 nm ;

[units at least once] 2

(b) 1. Each (pigment) absorbs a different wavelength of light ;

2. (more pigments) gives a greater range of absorption / plant able to absorblight of greater range of wavelengths ;

3. Reference to protective nature of carotenoids / accessory pigmentqualified ; 2

(c) 1. Use chromatography ;

2. {Grind up / crush / eq} sample of plant tissue in {propanone / organic solvent/ eq} ;

3. Place drops of {pigment / eq} on {paper / gel / column / silica} ;

4. Suspend paper in {test / boiling} tube with bottom touching solvent ;[allow from diagram]

5. {Time / eq} until pigments are seen to separate ; 4[8]

The carbohydrates in green plants are formed during the light-independent stage of photosynthesis. They are synthesised from glycerate 3-phosphate (GP).

(a) State precisely where the synthesis of carbohydrates takes place during the light-independent stage of photosynthesis.

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(b) Name the products of the light-dependent stage of photosynthesis used during the synthesis of carbohydrates.

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(c) Describe the role of ribulose bisphosphate (RuBP) in the light-independent stage of photosynthesis.

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(d) An investigation of photosynthesis in cells taken from a green alga was carried out.Samples of the algal cells were taken at 1 minute intervals over a period of 6 minutes.The quantities of GP and RuBP in these cell samples were measured.

At the start of the investigation, the algal cells were kept in an atmosphere with 1% carbon dioxide. After 3 minutes, the concentration of carbon dioxide was decreased to 0.003%.

The graph below shows the results of this investigation.

0 1 2 3 4 5 6

C arb o n d io x id e d ec reased

R u B P

G P

Q u an titie so f R u B Pan d G P/ a rb itra ryu n its

1 % ca rb o n d io x id e 0 .0 0 3 % ca rb o n d io x id e

Time / minutes

(i) Describe the effects of the decrease in the concentration of carbon dioxide on the quantities of GP and RuBP.

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(ii) Suggest explanations for the effects you have described in part (i).

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(Total 9 marks)

(a) Stroma of chloroplast / stroma 1

(b) NADPH / reduced NADP / NADPH2 / NADPH + H+ / NADPH + H;

ATP; 2

(c) Idea of carbon dioxide fixation / carbon dioxide acceptor;

To form 6C {compound / intermediate / molecule} / to form {2 × 3C molecules/ GP}; 2

(d) (i) RuBP increases and GP decreases;

Description of one curve (e.g. GP decreases and levels off, bothquantities equal at 3.5 minutes, comparison of 2 gradients); 2

(ii) 1. [RuBP rises because ] it is being regenerated / it accumulates / eq;

2. [RuBP rises because] less CO2 {to combine with it / forfixation / eq};

3. [GP falls because] less is being formed;

4. [GP falls because] being used faster than it’s being formed; 2[9]