heinemann biology 2 enhanced workbook - pearson australia

unit

Molecules of life

signatures of life

area of study 1

3 outcome 1

Analyse and evaluate evidence from practical investigations related to biochemical processes.

essential knowledge• The chemical nature of the cell:

– Synthesis of biomacromolecules: polysaccharides, nucleic acids and proteins

– The structure and function of lipids – The structure and function of DNA and RNA – The structure and functional diversity of proteins; the

proteome.

• The role of organelles and plasma membranes in the packaging and transport of biomolecules.

• The nature of biochemical processes: – Enzymes as organic catalysts – Energy requirements of cells; catabolic and anabolic

reactions – Energy transformations, including main stages in

and sites of photosynthesis and cellular respiration; ATP–ADP cycle; factors affecting rate of energy transformations.

• Applications of molecular biology in medicine, including the design of drugs, and in medical diagnosis.

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Biology 2 Student Workbook Copyright © Pearson Australia 2008 Copyright © Pearson Australia 2008 Unit 3 Area or Study 1: Molecules of life

Cells and the cell theory Cell theory

The cell theory is a foundation stone in the study of Biology. The cell theory states that:• Allorganismsaremadeupofcells.• Newcellsareproducedfromexistingcells.• The cell is the smallest organisational unit of a

living thing.

Therearetwodifferentkindsofcells—prokaryotic and eukaryotic.

Differences also occur within the group ofeukaryoticorganisms.Atypicalplant cell has cellulose cell wallsthatprovidestructuralsupport,chloroplasts thatarethesiteofphotosynthesis,andlarge vacuoles. Thesefeaturesarenotpresentinanimalcells.

Figure 3.1

(a) Plant cell, (b) Animal cell and (c) Bacterial cell

OrganellesThesearesubcellularstructureswithspecialisedfunctions:

BIOLOGICAL MOLECULES

ORGANIC

CARBOHYDRATES

• C, H, O • energy rich • cellular/respiration • structure role eg. cellulose/cell wall in plants • building blocks: carbohydrate polysaccharide composed of simple sugars (monosaccharides)

• C, H, O, N• enzymes• structural• carrier molecules eg. haemoglobin, protein channels in cell membranes• building blocks: amino acids

• C, H, O • fatty acids and glycerol • cell membrane structure • omega-3 fatty acids • building blocks: fatty acids and glycerol

• C, H, O, N, P • DNA and RNA • contain genetic information • cell reproduction • protein production • building blocks: nucleotides

• site of chemical reactions

• cellular respiration (aerobic)

• photosynthesis

• protein • nucleic acids

• enzyme ultra structure• phosphorous in DNA

PROTEIN

LIPIDS

NUCLEIC ACIDS

WATER

INORGANIC

NITROGEN

MINERALS CARBON DIOXIDE

OXYGEN

Biological moleculesThecellsthatmakeuplivingorganismsarethemselvescomposed of key chemical elements. Those whichoccuringreatestproportionincludecarbon,hydrogen,oxygenandnitrogen.Theseelementscombinetoform

avarietyofimportantbiomacromolecules.Biologicallyimportantmoleculescanbegroupedintotwotypes—organic and inorganic.

Figure 3.2

Chart of biological molecules.

(a) Plant cell (b) Animal cell

RIBOSOMES

NUCLEUS

PLASMAMEMBRANE

CYTOPLASM

GOLGIAPPARATUS

MITOCHONDRIA

CHLOROPLASTVACUOLE

CELL WALL

Table 3.2 Organelles and their functionsOrganelle Function

Nucleus Cell reproduction and control of cellular activities

Ribosomes Protein production

Mitochondria Aerobic respiration

Endoplasmic reticulum Transport of materials within cell

Golgi apparatus Protein production completed; proteins packaged for dispatch from cell

Cell wall Structural support in plants

Plasma membrane Encloses cell contents; regulates passage of materials into and out of cell

Cytoplasm Reservoir containing cell contents, including water, ions, dissolved nutrients, enzymes and organelles

Lysosomes Contain enzymes responsible for breakdown of debris

Vacuole Storage facility for fluid, enzymes, nutrients

Chloroplast Photosynthesis

Table 3.1 Cells and their features

Type of cell Feature Example

Eukaryote Distinct organelles such as ribosomes as well as membrane-bound organelles including nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles

Organisms in Kingdoms Protista, Fungi, Plantae, Animalia, but not Monera (bacteria, cyanobacteria)

Prokaryote Lack membrane-bound organelles; nuclear material present as a single, circular thread of DNA; cell membrane surrounded by cell wall of protein and complex carbohydrate; relatively small cells; feature circular threads of DNA called plasmids

Organisms in Kingdom Monera, i.e. bacteria, cyanobacteria (blue-green algae), archaeobacteria

PLASMIDS

BACTERIALCHROMOSOME

(c) Bacterial cell

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Key roles• Enclosecellcontents—maintainstructureofcell• Regulate the movement of materials into and

outof thecell—maintainadifferentcompositionwithin the cell compared with cell’s externalenvironment.

Membrane features• Protein receptors allow communication between

cells,forexample,byhormones,nerves,directcell-to-cellcontact;andallowcellrecognition.

Membrane compositionTheplasmamembraneiscomposedofaphospholipidbilayer (two layers of phospholipid molecules)embeddedwithmoleculesofproteinandcholesterol.

Phospholipid molecules have their hydrophobic tails directedintothecentreoftheplasmamembraneand their hydrophilic headsdirectedtowardsthefluidmediumoneithersideofthemembrane.

Proteinmoleculesserveaschannelsforfacilitateddiffusionandactivetransport.

Cholesterol molecules provide stability for themembrane.

Carbohydrate molecules associated with proteinsare involved in cell recognition.

The model of the plasma membrane is referredto as fluid-mosaicbecauseofthe‘fluid’natureofthephospholipidmoleculeswhicharefreetomoveaboutwithin the structure of each layer;‘mosaic’ refers tothe proteins scattered throughout the phospholipidlayers.

Plasma membranes

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protein cholesterol carbohydrate

phospholipid bilayer

protein channel

phospholipid molecule

hydrophobic end

hydrophilic end

Figure 3.3

3D fluid-mosaic model of the plasma membrane.

Table 3.3 Movement across the cell membrane

Process Description Active or passive

Diagram Example in organism

Diffusion Movement of particles from an area of high concentration to an area of low concentration, along a concentration gradient

Passive (does not require energy)

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Oxygen enters body cells (low in O2 since continually using O2 in cellular respiration) from the capillaries where it is in high concentration (O2 replenished at lungs)

Osmosis Special type of diffusion that involves movement of water molecules across a partially permeable membrane; water moves from an area of high concentration of free water molecules to an area of low concentration of free water molecules, i.e. low solute concentration to high solute concentration

Passive

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starchmolecule

watermolecule

Cells in kidney medulla absorb water by osmosis due to osmotic gradient between ion concentration in tissue fluid and the kidney tubules

Facilitated diffusion

Movement of particles from high to low concentration through protein channel in cell membrane

Passive

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protein channel

outside cell

inside cell

protein

Small molecules such as amino acids and glucose enter cell via protein channel

Active transport

Movement of particles from an area of relatively low concentration to an area of high concentration, against a concentration gradient

Active (requires input of energy)

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outsidecell

insidecell

ion

Uptake of ions by root hair cells of plants and uptake of nutrients by gut epithelium cells of animals, so that concentration within cells exceeds concentration in external medium

Movement across the membraneTheexchangeofmaterialsbetweencellsandtheirexternalenvironmentoccursthroughtheprocessesof:• diffusion• osmosis• facilitateddiffusion,or• activetransport.

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Metabolism and enzymesThe metabolismofanorganismisthesumofallthechemical reactions that occur within its cells. Thisincludes the energy-transforming reactions of cellssuchasproductionoforganicmolecules,breakdown,recycling and excretory processes. Such biochemicalprocessesareuniversal,thatis,theyoccurinthecellsof all living organisms to ensure the survival of theindividual.

Enzymes are biological catalysts—they increasethe rate of biochemical reactions in cells, e.g. thechemicalreactionsinvolvedincellularrespirationandphotosynthesis.

Properties of enzymes• composedofprotein• substrate specific—catalyse a chemical reaction

involvingaparticularsubstratemolecule,andnotanyother.Therearetwotheoriesusedtoexplainhowenzymesinteractwiththeirsubstrates.

1 Lock-and-key

2 Induced fit

• takepartinchemicalreactionsbutarenot used up or changedbytheprocess;releasedattheendofareaction and so are available to be used over and over again

• have optimal conditions under which they workmost effectively; will catalyse a reaction so thatmaximum product is produced per unit of time,e.g.optimaltemperaturefordigestiveenzymesinduodenumofhumansis37°CandpH8

• sensitivetofactorssuchastemperatureandpH— when these conditions are not optimal, theactivity of enzymes is reduced; extremesof suchfactorsmayleadtoenzymesbecomingdenatured;whenthishappenstheenzymecannotrecoveritsfunction because the shape of its active site hasbeenpermanentlyaltered.

Enzymesareusuallydenotedbythesuffix‘ase’,e.g.maltase,lactase,protease,amylase,lipase.

Therateofenzymeactivityisalsodependentuponthe:• concentration of substrate—the higher the

concentrationofthesubstrate,thegreatertherateof interaction between substrate molecules andenzymes,leadingtoincreasedrateofreaction

• concentration of enzyme—the more enzymeavailabletocatalyseareaction,themorerapidlyitwillproceeduntilallenzymesarefullyengagedinthe reaction.

Activation energy: energy expended to initiateenzyme-catalysed reaction; even catabolic reactionsrequireaninitialinputofenergytostartreaction

Coenzymes:smallorganicmoleculesimportanttothenormalfunctioningofenzymes,e.g.vitamins

Cofactors:inorganicionsimportanttothenormalfunctioningofenzymes,e.g.Mg++

Energy transformationsLiving organisms require energy for growth,movement,repairofdamagedtissueandreproduction.Energy isobtainedby theproductionofenergy-richorganiccompoundsinautotrophicorganismssuchasplants,andbytheconsumptionofplantsand/orotheranimals by heterotrophic organisms. Different kindsofenergytransformationsareinvolved.

Accessing energy-rich molecules: making ATPATP(adenosinetriphosphate)isthe immediate source of energy for cells.Itisproducedinaseriesofchemicalreactions that involves the breakdown of organicmolecules.TheuseableenergyofATPiscontainedinthephosphatebondsofthemolecule.ThecyclingofATP andADP (adenosine diphosphate) means thatenergy continues to be available for use in the cell.

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glucose

carbondioxideand water

energy

ADP

ATP

adenosine

phosphate

energy-containing bond

energyfor work

Cells access the energy available in organic molecules through glycolysis (anaerobic) and either cellular respiration (aerobic) or fermentation (anaerobic).

Cellular respirationistheprocessinwhichcomplexorganiccompoundsarebrokendowntoreleaseenergy(ATP).Waterisaby-product.

C6H12O6 + 6O2 → 6CO2 +6H2O+energy(36–38ATP)

Figure 3.7

ATP/ADP cycle.

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Cel

l

Glycolysis

Krebs cycle

Electron transfer inner membraneof mitochondria

inner compartmentof mitochondria

2 pyruvates 6 CO2

(each pyruvate 3 CO2

glucose 2 pyruvate

2 ATP

2 ATP

32 ATP

in cytosol

mito

chon

drio

n cy

toso

l

Figure 3.8

Energy release in presence of oxygen: glycolysis, Kreb’s cycle and electron transfer.

Figure 3.5

Rate of enzyme activity continues to increase with increasing temperature. Excessive temperature denatures enzymes and activity ceases.

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Temperature °C

Rate ofenzymeactivity

Figure 3.6

Rate of enzyme activity increases with increasing enzyme concentration.

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Enzyme concentration

Rate ofenzymeactivity

substrate product

active site

molecules

enzyme

enzyme–substratecomplex

Figure 3.4b

Model of enzyme ‘induced fit’ operation.

Figure 3.4a

Model of enzyme ‘lock-and-key’ operation.

substrate product

active site

molecules

enzyme

enzyme–substratecomplex

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Cytochromes are proteins involved in the processof electron transport on the inner membrane ofmitochondriaduringcellularrespiration.

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Glucose

animalslactic acid + 2 ATP

plants and yeast alcohol + CO2 + 2 ATP

Sincetheseprocessesinvolvetherelease of energy,they are called exergonic reactions. The release of energy is the result of the breakdown of organic compounds.Energy is releasedwhenchemicalbondsarebroken.Thesereactionsarecatabolic.

Building energy-rich molecules: photosynthesisThe ultimate source of energy for living things is the sun. Photosynthesis is the process in which green plantsuse chlorophyll to trap light energy and use it tocombinewaterandcarbondioxidetoproduceenergy-rich organic compounds (glucose). Oxygen is a by-product(Figure3.10).

Photosynthesisinvolvesthesynthesis of biomacro-molecules and is therefore described as anabolic. Sincethisprocessrequiresaninput of energy,itisanendergonic reaction.

light 6CO2+12H2O C6H12O6 +6O2+6H2O chlorophyll

Photosynthesistakesplaceinthechloroplastsandoccursinstepscalledthelight-dependent reaction and the light-independent reaction.

In contrast, respiration involves the chemicalbreakdownofglucoseincellsforthereleaseofenergy.This results in the uptake of O2 and the release of CO2.

Someautotrophicbacteriauseinorganicmaterialstobuildorganiccompoundswithouttheinvolvementof sunlight. This is called chemosynthesis.

C4 and CAM photosynthesisSomespeciesofplantsadapted tohotenvironmentshave different photosynthetic pathways. These aresolutions for plants that must have their stomataclosed formuchof theday toavoidexcessivewaterlossandsohavelesstimetoacquirecarbondioxideforphotosynthesis.C4plants,suchassugarcane,aremoreefficientatfixingcarbondioxidethanC3plants—theycapture more carbon dioxide per unit time (Figure3.12). The first stable carbon compound produced

Figure 3.9

Energy release in absence of oxygen.

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Grana — light-dependent reaction

12 H2O

Stroma — light-independent reaction

24 H+ + 6CO2 (Calvin cycle)

C6 H12 O6 + 6H2O

24 H+ + 6O2

Figure 3.11

Chloroplast—light-dependent and light-independent reactions.

Table 3.4 Factors that affect the rate of photosynthesis in green plants

Factor Effect

Carbon dioxide concentration

The higher the concentration gradient between the intercellular spaces and the external environment, the greater the diffusion rate of carbon dioxide into leaves via stomata, and, therefore, the greater the rate of photosynthesis

Light intensity The greater the light intensity, the greater the rate of photosynthesis, until the point at which other factors limit the process, e.g. high temperatures result in closed stomata

Temperature Increasing temperature results in increasing rate of photosynthesis, until optimal temperature for photosynthetic enzymes is reached; further increases in temperature result in decrease in photosynthetic rate

Water Water is a reactant in photosynthesis; it is also important in the turgidity of guard cells, keeping stomata open for entry of carbon dioxide. Reduced water availability decreases rate of photosynthesis

Chlorophyll Light-trapping pigment; larger amounts of chlorophyll mean more sunlight is harnessed, thereby increasing rate of photosynthesis

Oxygen Not directly involved in photosynthesis; however, high oxygen concentrations reduce rate of carbon fixation in photosynthesis

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PHOTOSYNTHESIScarbohydrates produced

RESPIRATIONcarbohydrates used

O2

O2

CO2

CO2

H2O

H2O

H2O

energy

Figure 3.10

Summary of photosynthesis and respiration.

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C3 Plant

C4 Plant

CO

2 ta

ken

up/u

nit

light

ene

rgy

abso

rbed

10 20

heat temp °C

30 40

Figure 3.12

Comparison of CO2 take up as measure of photosynthesis in C3 and C4 plants at increasing temperature.

containsfourcarbonatoms(henceC4photosynthesis).CAMplants,suchaspineapple,onlyhavetheirstomataopenduringthenight.Thecarbondioxidetheycollectis converted to crassulacean acid (called crassulacean acidmetabolism=CAM)whichisstoredduringthenight.Duringthedaywhenthestomataareclosed,thecarbondioxideisreleasedfromstorageandisavailabletotakepartinnormalC3photosynthesis.The factors affecting the rate of photosynthesis aresummarisedinFigure3.13andTable3.4.

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Temperature limits rate

High temperature

Low temperature

Light intensity

Rat

e of

pho

tosy

nthe

sis

Ligh

t lim

its ra

te

Figure 3.13

Effect of temperature and light intensity on rate of photosynthesis.

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04Enzyme ABC—amazing biological catalystsl1 Make a selection from the list below to fill in the missing words. This will give you a complete summary of enzymes and

their functions.

biomolecules deficiency substrate-specific optimal

denatured catabolic catalysts temperature

protein active site photosynthesis cellular respiration

metabolism anabolic coenzymes

Enzymes are biological . They increase the rate at which chemical reactions occur in living cells. They

are organic compounds composed of . Enzymes are important facilitators of energy-transforming

reactions, recycling processes, synthesis of some compounds and breakdown of others—all of the processes that make

up the of cells.

Enzymes are involved in both the construction and breakdown of . Chemical reactions in which

larger molecules are constructed from smaller ones are called reactions. is

an example that typically occurs in plant cells. reactions involve the breakdown of large molecules

into smaller ones. is an example of such a reaction in cells.

Enzymes are - , that is, they have an active site that fits a particular substrate

molecule only. This feature of enzymes is sometimes referred to as ‘lock-and-key’ or ‘induced fit’.

Enzymes have conditions, that is, they operate most efficiently under particular conditions.

Enzymes are sensitive to factors such as and pH. Their rate of activity can also be influenced

by the concentration of substrate or enzyme. Cofactors and also affect enzyme action.

The of an enzyme can be by excessive

temperatures or pH.

Enzyme can result in disease.

l2 Circle the word(s) that make the following statements about enzymes correct.

Enzymes are needed in small/large amounts.

Enzymes are used up/not used up in chemical reactions.

Enzymes can/cannot be used over and over again.

Enzymes do/do not affect the final amount of product in a reaction.

Enzymes increase/decrease the activation energy required to initiate reactions.

03Model membranesl1 The diagram represents a fluid-mosaic model of a plasma membrane. Complete the diagram by adding labels and

functions where indicated.

l2 Outline the features of plasma membranes that have led to their description as ‘fluid-mosaic’.

l3 Describe the role of the following molecules in plasma membranes:

a cholesterol:

b carbohydrate:

l4 Plasma membranes play an important role in exchange of materials into and out of cells. Complete the table outlining these processes and identify the components of plasma membranes involved in each.

Process Description of process Example of material exchanged

Component of plasma membrane involved

Simple diffusion

Facilitated diffusion

Osmosis

Active transport

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CHOLESTEROL

PHOSPHOLIPID MOLECULE

PROTEIN STRUCTURE:FUNCTION:

Figure 3.18

Fluid-mosaic model of a plasma membrane.

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Activation energyChemical reactions need a minimum energy input to ‘kick start’ them. This is called the activation energy of the reaction. Enzymes reduce the amount of energy needed to provide this kick start.

In the reaction in Figure 3.19, a more complex molecule is being constructed from two simpler ones. This involves a change in energy (∆G) from an initial low level of energy to a final higher state. That is, there has been an overall input of energy into this reaction to construct the larger molecule. The energy that has been channelled into the reaction is contained within the chemical bonds that hold the two sugar subunits together. This reaction is called an endergonic reaction.

Graph A shows the activation energy for the sucrose-building reaction.

The same enzyme catalyses the breakdown of sucrose into glucose and fructose in an exergonic reaction.

Complete Graph B to illustrate the activation energy for this reaction.

l7 Why is the reaction in Graph B described as exergonic?

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Totalenergy

COURSE OF REACTION

FINALSTATE

INITIALSTATE

G∆

Figure 3.20

Activation energy

Active enzymes Enzyme action

Enzymes catalyse chemical reactions in cells in two directions, that is, the reactions are reversible. The example below illustrates an enzyme catalysing the production of the disaccharide (two sugar) sucrose from the simple sugars glucose (G) and fructose (F).

l1 Complete the diagram by inserting the glucose and fructose molecules into the active site of the enzyme. Then draw the newly constructed molecule of sucrose after it is released from the enzyme.

Use coloured pencils to colour-code your diagram. Use different colours for each of the different kinds of sugar molecule and for the enzyme.

l2 Explain why the relationship between enzymes and their substrates is described as ‘lock-and-key’.

l3 Name two factors that can affect the active site of enzymes.

l4 Describe what happens to the active site of an enzyme if it is denatured. What are the consequences for enzyme activity when this occurs?

l5 Outline what is meant by the ‘induced fit’ model. Use a diagram to illustrate.

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ENZYME

GF

Figure 3.19

Active site of enzyme.

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Totalenergy

COURSE OF REACTION

Graph A: Endergonic Graph B: Exergonic

l6

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Partially permeable membranes

purpose

To investigate the effect of a partially permeable membrane on the movement of particles in solution.

background information

To test for the presence of starch, add a few drops of iodine/potassium iodide solution to the test solution. If starch is present the solution will change to a blue-black colour.

To test for the presence of glucose, dip a Clinistix into the test solution. If glucose is present, the Clinistix will change from pink to purple.

materials

• dialysis tubing• iodine/potassium iodide• Clinistix• 5% starch solution• glucose solution• thistle funnel• 2 gas jars• retort stand and clamp• test tubes• test tube rack• rubber bands• 50 mL beaker

procedure

APresenting partial permeability

1 Pour glucose solution into a 50 mL beaker to a depth of about 1 cm. Dip in one end of a piece of testape.

l1 Describe your observations.

2 Fill a gas jar with water until it is about three-quarters full. Test the water in the same way with a piece of testape.

l2 a Note the result.

b Explain why you have tested the water in the gas jar with testape.

3 Use the equipment listed to construct an experimental set-up similar to the one shown in Figure 3.29.

Set up the retort stand to support the thistle funnel first. Then secure the dialysis tubing. Moistening the dialysis tubing will help to open the ends. Tie one end firmly closed with a rubber band. Tie the other end so that it is securely fastened to the thistle funnel. Gently pour glucose solution into the thistle funnel until the level rises about 2 cm up the stem of the funnel. Place the gas jar beneath the thistle funnel. Use the clamp to lower the dialysis tubing completely into the water solution. Leave the set-up undisturbed for 30 minutes (longer if possible).

l3 a Use the Clinistix to once again test the solution in the gas jar. Describe your observations.

b Explain what has happened.

thistlefunnel

level of glucose soln in thistle funnel

cellulose bagfastened tothistle funnelwith rubber band

gas jar ormeasuringcylinder

retort standand clamp

cellulose bag filled with glucose solution

Figure 3.29

Equipment set-up for experiment.

Hypothetical halitosis—a proteomics simulationYou are a science graduate recently employed at a pathology clinic that specialises in proteomics. Your first assignment is to process saliva samples from volunteers taking part in trials designed to diagnose and treat individuals with chronic halitosis (bad breath).

It is found that degrees of bad breath are influenced by the presence of particular proteins in body fluids. A sample of sweat or saliva can be used to determine the presence of these proteins. Six subjects have volunteered their services and saliva.

Testing procedure: A drop of saliva is placed in each well of a SPIT card (Salivary Protein Indicator Test). Each well contains an indicator that tests for the presence of a specific protein.

The proteins that have been identified in saliva are:

• JM—linked to strong, unsavoury odour

• PU—linked to strong, unsavoury odour

• TP—fresh smelling odour, so named due to its similarity to toothpaste

• NS—a neutral protein linked to no smell

The effect of the different proteins is cumulative, so that the presence of more than one protein in the saliva of an individual increases the magnitude of the halitosis. On the other hand, protein TP appears to proportionally negate or cancel out the effect of an undesirable protein, e.g. TP cancels effect of PU.

The SPIT results for the six volunteers are shown in Figure 3.28, together with a standard against which the test cards are assessed.

Shaded wells indicated the presence of the protein in question.

Unshaded wells indicate the protein is not present.

l1 a Two individuals share the ranking of most acute halitosis. List these individuals.

b These two individuals have different SPIT results. Explain how the degree of halitosis can be the same.

l2 Subject 4 tests positive for three salivary proteins but has more pleasant breath than subject 1. Explain these results.

l3 Subjects 3 and 6 are competing for the same date. Based on SPIT results alone, decide which subject is more likely to be successful. Explain your choice.

l4 Rank the subjects in order from highest to lowest degree of halitosis.

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STANDARD

SUBJECT 1

SUBJECT 2

SUBJECT 3

SUBJECT 4

SUBJECT 5

SUBJECT 6

JM PU TP NS

Figure 3.28

Salivary protein testcards and standard.

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Modelling osmosisProcedure procedure

1 Pour starch solution into a test tube to a depth of about 1 cm. Add a few drops of iodine/potassium iodide solution.

l4 Describe any colour change that occurs.

2 Fill the second gas jar with water until it is about three-quarters full. Add several drops of iodine/potassium iodide solution.

l5 a What colour is the solution?

b What does the colour of the solution indicate about the presence of starch?

3 Use the equipment listed to construct an experimental set-up similar to the one shown in Figure 3.30(a).

Prepare the set-up in the same way as you did for Part A, except that this time you will pour starch solution into the thistle funnel/dialysis tubing. Place the gas jar beneath the thistle funnel. Lower the dialysis tubing completely into the water and iodine/potassium iodide solution. Leave the set-up undisturbed for 30 minutes (longer if possible).

conclusions

In this activity, you considered evidence that indicates some kinds of molecules move across partially permeable membranes while others do not.

Write the definition for:

l9 a osmosis

b diffusion

l10 Explain why some kinds of molecules are able to pass through partially permeable membranes and others are not. Use specific examples.

B

level of starchin thistle funnel

iodine/potassiumiodide and water

cellulose bagfilled withstarch solution(a)

Figure 3.30

Equipment set-up—(a) before, (b) after.

(b)

l6 Use coloured pencils to colour Figures 3.30(a) and 3.30(b) to reflect your observations at the start of the activity and again after 30 minutes.

l7 Describe any changes you observe.

l8 Account for the colour changes you have observed. Where did the molecules of water, iodine/potassium iodide and starch begin and where did they move to?

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Proteomic patterns and disease diagnosis—Tandem Mass Spectroscopy (TMS)Proteomics is the study of the proteins produced by an organism and includes the structure, function and interactions of the proteins. Tandem Mass Spectroscopy, one of the techniques available to analyse these proteins, is used to sort different kinds of molecules according to their molecular weight. In this case, the resulting proteomic pattern reveals differences between the levels of the amino acids phenylalanine and tyrosine.

In the Guthrie test, a blood sample to be analysed by TMS is the ‘sample data’. The proteomic pattern for the sample data is compared to standard data for ‘normal’ blood proteins.

The pattern of proteins present can be presented graphically. Analysis of the pattern of peaks provides information useful in making a diagnosis. During TMS, all the different amino acids present in the blood serum are separated according to molecular weight. Bioinformatic software is used to manipulate the data into graphical form. The graphs below include only the data relevant to phenylalanine and tyrosine.

l1 Describe the proteomic pattern for the amino acids phenylalanine and tyrosine for an individual with normal protein production.

l2 How does the sample data shown compare with the standard in this case?

l3 What does the data infer about the infant to whom the sample data belongs?

l4 Use the graphical data and your understanding of enzymes to account for the different blood serum levels of the amino acids phenylalanine and tyrosine in:

a the individual represented by the standard.

b the individual identified with PKU.

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AMINO ACIDS

BLOODSERUMLEVEL

OF AMINOACIDS

PHENYLALA

NINE

TYROSIN

E AMINO ACIDS

BLOODSERUMLEVEL

OF AMINOACIDS

PHENYLALA

NINE

TYROSIN

E

Graph A: Standard data Graph B: Sample data

Figure 3.33

Graphs comparing standard data and sample data for amino acids phenylalanine and tyrosine.

Double-take enzymesLook carefully at the flowchart illustrating the biochemical pathways involved in the metabolism of the amino acids phenylalanine and tyrosine.

l5 What kind of biomolecule is:

a phenylalanine:

b phenylalanine hydroxylase:

c tyrosine:

d tyrosinase:

l6 Outline the importance of these biomolecules in normal body functioning.

l7 The flowchart clearly indicates that PKU patients do not convert phenylalanine to tyrosine. Despite this, PKU patients are not necessarily albino. Explain why this is so.

l8 Outline the health implications for a person born with albinism.

l9 Suggest lifestyle strategies that will be important to an albino to minimise health risks related to their condition.

152C_HB2W

DIETARY PROTEIN

digested to

PHENYLALANINE

no phenylalaninehydroxylase

phenylalaninehydroxylaseproduced

TYROSINE

accumulationof phenylalanineor phenylpyruvic

acid

PHENYLKETONURIA

notyrosinase

tyrosinaseproduced

ALBINISM MELANIN

• brain damage if not under dietary management

• lack of pigment in skin, eyes, hair | pale appearance

• variations in depth / shade of skin, hair, eye colour

Figure 3.34

Flowchart of biochemical pathways—phenylalanine, tyrosine.

Sample

page

s

heinemann biology 2 enhanced workbook - pearson australia

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