AQA A LEVEL BIOLOGY PAPER 1 QUESTION PAPER
2025 (7402/1) AND ANSWERS
Describeyhowyyouywouldyuseyaybiochemicalytestytoyshowythatyaysolutionycontainedyaynon-
reducingysugar,ysuchyasysucrose.y[3]y-
yCORRECTyANSWERS,firstyreducingysugarsytest;yboilywithydiluteyHClyacidythenyNeutralisey
withyNaHCǑ,yaddybenedictyandyheatytoy95ydegreesyCybrickyredypptyformsyifyreducingysugaryi
sypresent
Describeyaychemicalytestyyouycouldycarryyoutytoyshowythatyaypieceyofycoconutycontainsylipid
s.y[3]y-
yCORRECTyANSWERS(Crushyin)yethanoly/yalcohol;yAddy(to)ywatery(Orderyofyaddingyisycriti
calyforythisypoint);yEmulsiony/ywhiteycolour
Explainywhatyisymeantybyyaypolymer.y[1]y-
yCORRECTyANSWERSMolecule)ymadeyupyofymanyyidentical/similarymolecules/monomer
s/ysubunits;
Nameytheyreactionywhichyoccursywhenystarchyisybrokenydownyintoymaltose.y[1]y-
yCORRECTyANSWERSHydrolysis
Whatyisytheyformulayforylactose?y[2]y-yCORRECTyANSWERSC12y;yH22Ō1
Describeyhowyβ-glucoseymoleculeydiffersyfromyaymoleculeyofyα-glucose.y[1]y-
yCORRECTyANSWERSHyatytopyrightyendy(insteadyofyOH)y/yOHyatybottomy(carbony1)
Showytwoywaysyinywhichytheystructureyofycelluloseyisydifferentyfromytheystructureyofystarch.y[
2]y-
yCORRECTyANSWERSStarchy1,4yandy1,6ybondsy/ybranchingyCellulosey1,4ybondsy/ynoy1,6y
bondsy/ystraight;ystarchyAllyglucosesy/monomersysameywayyupycelluloseyAlternateyglucose
syupsideydown;ystarchyHelixy/ycoiled/compactycelluloseyStraight;yStarchymonomeryAlphaygl
ucoseyCelluloseymonomeryBetayglucose
Describeytheystructureyofystarchyandyexplainyhowyitsystructureyisyrelatedytoyitsyfunction.y[3]y-
yCORRECTyANSWERSFormedyfromyαyglucose;yJoinedybyycondensation/ybyytheyremovaly
ofyaywaterymolecule/yglycosidicybonds;yBetweeny(carbons)y1yandy4y(andy1yandy6);yCoiledych
ain;ycompact;y(Allows)ystorageyofylargeyamountyinyaysmallyspace;yInsolubleysoyhasynoyeffect
yonyosmosis/waterypotential;yBranches;y(Allows)yrapidybreakdown/releaseyofyglucosey/yhyd
rolysis;
Theystructureyofyayphospholipidymoleculeyisydifferentyfromythatyofyaytriglyceride.yDescribeyh
ow.y[2]y-
yCORRECTyANSWERStriglycerideyhasythreeyfattyyacidsyandyphospholipidyhasytwo;ynoypho
sphateygroupypresentyinytriglycerideybutypresentyinyphospholipid.
Whatyisyanyunsaturatedyfattyyacid?y[1]y-
yCORRECTyANSWERSSomey/ytwoycarbonsywithyonlyyoneyhydrogeny/y(doubleybonds)ybetw
eenycarbonyatomsy/ynotysaturatedywithyhydrogen;
Describeytheystructureyofycelluloseyandyexplainyhowyitsystructureyisyrelatedytoyitsyfunction.y[3
]y-yCORRECTyANSWERSAlternateyβ-
glucoseyrotatedy180o,ylongystraightychains,yManyyhydrogenybondsyjoiny(polysaccharide)ych
ains/moleculesytoyeachyothery/ymakesymicrofibrilsy/ygivesytensileystrength;
Whichyelementsyareyfoundyinyproteins?y[1]y-
yCORRECTyANSWERSCarbon,yhydrogen,yoxygen,ynitrogeny(sometimesysulphur)
,Describeyhowyyouywouldyuseyaybiochemicalytestytoyshowythatyaysolutionycontainedyprotein.y[
2]y-yCORRECTyANSWERSBiurety/yalkaliy+ycopperysulphate;yLilac/purple/mauve/violet;
Whichybondsyareyfoundyinya)Primaryystructurey[1]b)Secondaryystructurey[1]yc)Tertiaryystruc
turey[2]y-
yCORRECTyANSWERSa)Peptideyb)yHydrogeny(andypeptide)yc)Ionic,ydisulphideybridges,y
hydrophobicyinteractionsy(hydrogenyandypeptide)
Explainyhowyaychangeyinytheyprimaryystructureyofyayglobularyproteinymayyresultyinyaydifferent
ythree-dimensionalystructure.y[3]y-
yCORRECTyANSWERSSequence yofyaminoyacidsychanges;ytertiaryystructureychanges/fold
syinyaydifferentyway;ybondsyformyinydifferentyplacesy(notypeptide);
Describeyhowytwo-wayychromatographyyisycarriedyout.y[2]y-
yCORRECTyANSWERSRunychromatogramythenyturnythroughy90/rightyangle;yWithyaydiffer
entysolvent;
Explainytheyadvantageyofyusingytwo-
wayychromatographyytoyseparateyshortypolypeptides.y[2]y-
yCORRECTyANSWERSSpreadsyspots/polypeptidesyoutymore/ymakeysureyspotyonlyycontai
nsyoneysubstance;
Explainyhowyinhibitorsyaffectytheyrateyofyenzyme-controlledyreactions.y[6]y-
yCORRECTyANSWERSStatementyaboutytwoytypes,ycompetitiveyandynon-
competitive;yCompetitive:ySimilaryshapeytoysubstrate;Inhibitorycanyenter/bindywithyactiveysit
ey(ofyenzyme);Non-
competitive:yAffect/bindytoyenzymeyotherythanyatyactiveysite;yDistortsyshapeyofyactiveysite;yI
nhibitors:yPreventyentryyof/bindingyofysubstrateytoyactiveysite;yThereforeyfewer/noyenzyme-
substrateycomplexesyformed;
Describeyandyexplainyhowyanyincreaseyinytemperatureyaffectsytheyrateyofyanyenzymeycontro
lledyreaction.y[5]y-
yCORRECTyANSWERSRateyofyreactionyincreases;yIncreasingytemperatureyincreasesyrate
yofymovementyofymolecules/ykineticyenergy;yCollideymoreyoften/substrateyentersyactiveysitey
moreyoften/moreyenzyme-
substrateycomplexesyformed;yUpytoyoptimum;yRateyofyreactionydecreases;yHighytemperatu
resycauseydenaturation/lossyofytertiaryystructure/3Dystructure;yByybreakingyspecifiedybonds
y(notypeptideybond);yActiveysiteyaltered/substrateycannotybind/fit/
Anyenzymeycatalysesyonlyyoneyreaction.yExplainywhyy[2]y-
yCORRECTyANSWERS(Enzymeyhas)yactiveysite;yOnlyysubstrateyfitsy(theyactiveysite);
Describeytheyinducedyfitymodelyofyenzymeyaction.y[2]y-
yCORRECTyANSWERSActiveysitey/yenzymeynotycomplementary;yActiveysiteychangesy(sha
pe)y/yisyflexible;y(Changeyinyenzymeyallows)ysubstrateytoyfity/yE-Sycomplexytoyform;
Describeyoneywayythatytheylockyandykeyymodelyisydifferentyfromytheyinducedyfitymodel.y[1]y-
yCORRECTyANSWERSActiveysiteydoesynotychangey(shape)y/yisyfixedy(shape)y/yisyrigidy/ydo
esynotywrapyaroundysubstratey/y(already)yfitsytheysubstratey/yisycomplementaryy(beforeybindi
ng);
ExplainywhyytheyrateyofyreactionyofyanyenzymeyisylowyawayyfromyitsyoptimumypH.y[3]y-
yCORRECTyANSWERS(changeyinypH)yleadsytoybreakingyofybondsyholdingytertiaryystructur
e/ychangesychargeyonyaminoyacids;yenzyme/protein/activeysiteylosesyshape/denatured;ysu
bstrateywillynotybindywith/fityactiveysite;yfewer/noyESycomplexesyformed;
,Ayproteinymoleculeycontainsy150yaminoyacids.yWhatyisytheytotalynumberyofypeptideybondsyin
ythisymolecule?y[1]y-yCORRECTyANSWERS149
Howydoyyouycalculateymagnification?y[1]y-
yCORRECTyANSWERSM=yIy(Image)/yAy(actualysize)
Describeytheywaysyinywhichyprokaryoticycellsyandyeukaryoticycellsydiffer.y[3]y-
yCORRECTyANSWERSProkaryoticycellsydoynotyhaveyaynucleusy/yhaveygeneticymaterialyiny
cytoplasm;yDNAyinyloopy/yring;yNotyassociatedywithyproteinsy/ydoynotyhaveychromosomesy/c
hromatiny/ydoynotydivideybyymitosis;ySmalleryribosomes;yNoymembrane-
boundyorganelles;ySuchyasymitochondriay/ylysosomesy/yendoplasmicyreticulumy/yGolgiy/ychl
oroplasts;yProkaryoticycellsymayyhaveymesosomes;yProkaryoticycellsysmaller;yMayybeyencl
osedybyycapsule;
Whatyisytheyfunctionyof:ya)Ribosomeyb)SmoothyERyc)Golgiyapparatusyd)yChloroplastye)Mit
ochondriay[5]y-
yCORRECTyANSWERSa)Proteinysynthesisyb)Lipidysynthesisyandytransportyc)Processingy
andypackagingyproteinsyforysecretionyd)Photosynthesisye)AerobicyrespirationytoyproduceyA
TP
Explainytheyadvantagesyandylimitationsyofyusingyaytransmissionyelectronymicroscopey[5]y-
yCORRECTyANSWERSAdvantages: ySmallyobjectsycanybeyseen;yTEMyhasyhighyresolutiony
asywavelengthyofyelectronsyshorter;yLimitations:yCannotylookyatylivingycellsyasycellsymustybe
yinyayvacuum;ymustycutysectiony/ythinyspecimen;yPreparationymayycreateyartefact;yDoesynoty
producey3Dyorycoloredyimage;
Whyyanyelectronymicroscopeycanybeyusedytoyproduceyimagesy[2]y-
yCORRECTyANSWERSEMygivesyhighyresolutionydueytoyshortywavelengthyofyelectrons;
Explainyhowyvirusesycauseydamageytoycells.y[3]y-
yCORRECTyANSWERSusesy/ybreaksyupy/ydigestsyhostynucleary/ygeneticymaterialy(allowyref
erencesymadeytoyDNAy/RNAyinsteadyofynucleary/genetic);yvirusyDNAy/ygeneticymaterialyinse
rtedyintoyhostsyDNAy/ychromosomey/ygeneticymaterial;yhostycellsyaminoyacidsyareyusedytoysy
nthesizeyviralyproteins;ycellylysis;ybyyenzymey(producedybyyexpressingyayvirusygene);ytoxiny
production;
Describeyandyexplainyhowycellyfractionationyandyultracentrifugationycanybeyusedytoyisolatey
mitochondriayfromyaysuspensionyofyanimalycells.y[5]y-
yCORRECTyANSWERSCellyhomogenisationytoybreakyopenycells;y1.yAcceptysuitableymeth
odyofybreakingyopenycells.yFilterytoyremovey(large)ydebrisy/ywholeycells;y2.yRejectyremovesyc
ellywalls.yUseyisotonicysolutionytoypreventydamageytoymitochondriay/yorganelles;yKeepycoldyt
oypreventy/yreduceydamageybyyenzymesy/yuseybufferytoypreventyproteiny/yenzymeydenaturati
on;yCentrifugey(atyloweryspeedy/y1000yg)ytoyseparateynucleiy/ycellyfragmentsy/yheavyyorganel
les;yRe-
spiny(supernatanty/yafterynucleiy/ypelletyremoved)yatyhigheryspeedytoygetymitochondriayinypell
ety/yatybottom.
Nameytwoystructuresypresentyinyeukaryoticycellsythatyareynotypresentyinytheycellsyofyprokary
otes.y[2]y-
yCORRECTyANSWERSNucleus;ymitochondria;ychloroplast,yGolgi,yRER;ySER;ycentrioles
Describeytheyfluid-mosaicystructureyofyaycellysurfaceymembrane.(5/8ymarks)y-
yCORRECTyANSWERSPhospholipids yandyproteins;yPhospholipidybilayer;yArrangementyof
yphospholipidymoleculesy'Tailsytoytails';'Floating'(protein)ymoleculesy/ymoleculesycanymovey
inymembrane;Intrinsicyproteinsyextendythroughybilayer;yExtrinsicyproteinsyinyouterylayeryonl
, y;(Ref.ytoyintrinsicyandyextrinsic,yunqualified,ygainsy1ymark);Detailyofychannelyproteinsy/yprot
einyshapesy/yglycoproteins;Presenceyofycholesterolybetweenyphospholipids.
Describeytheypartyplayedybyycellysurfaceymembranesyinyregulatingytheymovementyofysubsta
ncesyintoyandyoutyofycells.(6/10ymarks)y-yCORRECTyANSWERS1.yNon-
polar/lipidysolubleymoleculesymoveythroughyphospholipidylayer/bilayer;2.ySmallymolecules/
water/gasesymoveythroughyphospholipidylayer/bilayer;3.yIons/waterysolubleysubstancesym
oveythroughychannelsyinyproteins;4.ySomeyproteinsyareygated;5.yReferenceytoydiffusion;6.C
arriersyidentifiedyasyproteins;7.yCarriersyassociatedywithyfacilitatedydiffusion;8.yCarriersyass
ociatedywithyactiveytransport/transportywithyATP/pumps;9.yDifferentycellsyhaveydifferentypro
teins;10.yCorrectyreferenceytoycytosis;
Describeytheyroleyofytheyenzymesyofytheydigestiveysystemyinytheycompleteybreakdownyofysta
rch.y(6ymarks)y-
yCORRECTyANSWERS1.yAmylase;2.y(Starch)ytoymaltose:3.yMaltase;4.yMaltoseytoyglucos
e;5.yHydrolysis;6.y(Of)yglycosidicybond;
Explainyhowytheysmallyintestineyisyadaptedytoyitsyfunctionyinytheyabsorptionyofytheyproductsy
ofydigestion.y(6/9ymarks)y1.y-
yCORRECTyANSWERSLargeysurfaceyareayprovidedybyyvilliy/ymicrovilli;2.ylongy/yfoldsyincre
aseysurfaceyareay/ytimeyforyabsorption;3.ythinyepithelium;4.yshortydiffusionypathway;5.ycapill
aryynetworkyabsorbsyaminoyacidsy/ysugars;6.ylactealyforyabsorptionyofydigestedyfats;7.yMain
tainsyaysteepyconcentrationygradient;8.ymitochondriaysupplyyATPy/yenergyyforyactiveytransp
ort;9.ycarrieryproteinsy(inymembranes);
Describeyandyexplainytheyroleyofydiffusionyinytheyabsorptionyofydigestedyfoodybyytheyileum.y(
4ymarks)y-
yCORRECTyANSWERS1.ymovementyalongy/ydownyconcentrationygradient;2.ymonoglyceri
desy/ymicelles/fattyyacidsymoveyintoyepithelialycells;3.ymonoglyceridesymoveyfromyepitheliu
myintoyblood;4.ychylomicronsymoveyintoylactealsy/ylymph;
Describeyandyexplainytheyroleyofyfacilitatedydiffusionyinytheyabsorptionyofydigestedyfoodybyyt
heyileum.y(3ymarks)y-
yCORRECTyANSWERS1.ymovementyalongy/ydownyconcentrationygradient;2.yreferenceytoy
carriery/ychannelyproteins;3.ymonosaccharidesyorynamedy/yaminoyacidsymoveyintoyepithelial
ycells;
Describeyandyexplainytheyroleyactiveytransportyinytheyabsorptionyofydigestedyfoodybyytheyileu
m.(4/6ymarks)y-
yCORRECTyANSWERS1.ymovementyagainstyconcentrationygradient;2.yenergyy/yATPyrequ
ired;3.yreferenceytoycarrieryproteins;4.ymonosaccharidesyorynamedy/yaminoyacidsymovedyin
toyepithelialycells;5.yreferenceytoyco-
diffusionye.g.yglucoseyandyNaCl;6.ymonosaccharidesyorynamedy/yaminoyacidsymoveyintoybl
ood
DescribeyhowytheystructureyofyDNAyisyrelatedytoyitsyfunctiony(4/7marks)y-
yCORRECTyANSWERS1.ySugar-
phosphateybackbone:yprovidesystabilityy&yprotectsybasesy2.yDoubleystranded:yreplicationyc
anyoccurysemi-
conservativelyywhereyeachystrandycanyactyasytemplateymakingyreplicationymoreyaccuratey3
.yComplementaryybaseypairingy(A-TyandyG-
C)ymakesyreplicationymoreyaccuratey4.yIndividualyhydrogenybondsyareyweak:yeasilyyunzipy
2025 (7402/1) AND ANSWERS
Describeyhowyyouywouldyuseyaybiochemicalytestytoyshowythatyaysolutionycontainedyaynon-
reducingysugar,ysuchyasysucrose.y[3]y-
yCORRECTyANSWERS,firstyreducingysugarsytest;yboilywithydiluteyHClyacidythenyNeutralisey
withyNaHCǑ,yaddybenedictyandyheatytoy95ydegreesyCybrickyredypptyformsyifyreducingysugaryi
sypresent
Describeyaychemicalytestyyouycouldycarryyoutytoyshowythatyaypieceyofycoconutycontainsylipid
s.y[3]y-
yCORRECTyANSWERS(Crushyin)yethanoly/yalcohol;yAddy(to)ywatery(Orderyofyaddingyisycriti
calyforythisypoint);yEmulsiony/ywhiteycolour
Explainywhatyisymeantybyyaypolymer.y[1]y-
yCORRECTyANSWERSMolecule)ymadeyupyofymanyyidentical/similarymolecules/monomer
s/ysubunits;
Nameytheyreactionywhichyoccursywhenystarchyisybrokenydownyintoymaltose.y[1]y-
yCORRECTyANSWERSHydrolysis
Whatyisytheyformulayforylactose?y[2]y-yCORRECTyANSWERSC12y;yH22Ō1
Describeyhowyβ-glucoseymoleculeydiffersyfromyaymoleculeyofyα-glucose.y[1]y-
yCORRECTyANSWERSHyatytopyrightyendy(insteadyofyOH)y/yOHyatybottomy(carbony1)
Showytwoywaysyinywhichytheystructureyofycelluloseyisydifferentyfromytheystructureyofystarch.y[
2]y-
yCORRECTyANSWERSStarchy1,4yandy1,6ybondsy/ybranchingyCellulosey1,4ybondsy/ynoy1,6y
bondsy/ystraight;ystarchyAllyglucosesy/monomersysameywayyupycelluloseyAlternateyglucose
syupsideydown;ystarchyHelixy/ycoiled/compactycelluloseyStraight;yStarchymonomeryAlphaygl
ucoseyCelluloseymonomeryBetayglucose
Describeytheystructureyofystarchyandyexplainyhowyitsystructureyisyrelatedytoyitsyfunction.y[3]y-
yCORRECTyANSWERSFormedyfromyαyglucose;yJoinedybyycondensation/ybyytheyremovaly
ofyaywaterymolecule/yglycosidicybonds;yBetweeny(carbons)y1yandy4y(andy1yandy6);yCoiledych
ain;ycompact;y(Allows)ystorageyofylargeyamountyinyaysmallyspace;yInsolubleysoyhasynoyeffect
yonyosmosis/waterypotential;yBranches;y(Allows)yrapidybreakdown/releaseyofyglucosey/yhyd
rolysis;
Theystructureyofyayphospholipidymoleculeyisydifferentyfromythatyofyaytriglyceride.yDescribeyh
ow.y[2]y-
yCORRECTyANSWERStriglycerideyhasythreeyfattyyacidsyandyphospholipidyhasytwo;ynoypho
sphateygroupypresentyinytriglycerideybutypresentyinyphospholipid.
Whatyisyanyunsaturatedyfattyyacid?y[1]y-
yCORRECTyANSWERSSomey/ytwoycarbonsywithyonlyyoneyhydrogeny/y(doubleybonds)ybetw
eenycarbonyatomsy/ynotysaturatedywithyhydrogen;
Describeytheystructureyofycelluloseyandyexplainyhowyitsystructureyisyrelatedytoyitsyfunction.y[3
]y-yCORRECTyANSWERSAlternateyβ-
glucoseyrotatedy180o,ylongystraightychains,yManyyhydrogenybondsyjoiny(polysaccharide)ych
ains/moleculesytoyeachyothery/ymakesymicrofibrilsy/ygivesytensileystrength;
Whichyelementsyareyfoundyinyproteins?y[1]y-
yCORRECTyANSWERSCarbon,yhydrogen,yoxygen,ynitrogeny(sometimesysulphur)
,Describeyhowyyouywouldyuseyaybiochemicalytestytoyshowythatyaysolutionycontainedyprotein.y[
2]y-yCORRECTyANSWERSBiurety/yalkaliy+ycopperysulphate;yLilac/purple/mauve/violet;
Whichybondsyareyfoundyinya)Primaryystructurey[1]b)Secondaryystructurey[1]yc)Tertiaryystruc
turey[2]y-
yCORRECTyANSWERSa)Peptideyb)yHydrogeny(andypeptide)yc)Ionic,ydisulphideybridges,y
hydrophobicyinteractionsy(hydrogenyandypeptide)
Explainyhowyaychangeyinytheyprimaryystructureyofyayglobularyproteinymayyresultyinyaydifferent
ythree-dimensionalystructure.y[3]y-
yCORRECTyANSWERSSequence yofyaminoyacidsychanges;ytertiaryystructureychanges/fold
syinyaydifferentyway;ybondsyformyinydifferentyplacesy(notypeptide);
Describeyhowytwo-wayychromatographyyisycarriedyout.y[2]y-
yCORRECTyANSWERSRunychromatogramythenyturnythroughy90/rightyangle;yWithyaydiffer
entysolvent;
Explainytheyadvantageyofyusingytwo-
wayychromatographyytoyseparateyshortypolypeptides.y[2]y-
yCORRECTyANSWERSSpreadsyspots/polypeptidesyoutymore/ymakeysureyspotyonlyycontai
nsyoneysubstance;
Explainyhowyinhibitorsyaffectytheyrateyofyenzyme-controlledyreactions.y[6]y-
yCORRECTyANSWERSStatementyaboutytwoytypes,ycompetitiveyandynon-
competitive;yCompetitive:ySimilaryshapeytoysubstrate;Inhibitorycanyenter/bindywithyactiveysit
ey(ofyenzyme);Non-
competitive:yAffect/bindytoyenzymeyotherythanyatyactiveysite;yDistortsyshapeyofyactiveysite;yI
nhibitors:yPreventyentryyof/bindingyofysubstrateytoyactiveysite;yThereforeyfewer/noyenzyme-
substrateycomplexesyformed;
Describeyandyexplainyhowyanyincreaseyinytemperatureyaffectsytheyrateyofyanyenzymeycontro
lledyreaction.y[5]y-
yCORRECTyANSWERSRateyofyreactionyincreases;yIncreasingytemperatureyincreasesyrate
yofymovementyofymolecules/ykineticyenergy;yCollideymoreyoften/substrateyentersyactiveysitey
moreyoften/moreyenzyme-
substrateycomplexesyformed;yUpytoyoptimum;yRateyofyreactionydecreases;yHighytemperatu
resycauseydenaturation/lossyofytertiaryystructure/3Dystructure;yByybreakingyspecifiedybonds
y(notypeptideybond);yActiveysiteyaltered/substrateycannotybind/fit/
Anyenzymeycatalysesyonlyyoneyreaction.yExplainywhyy[2]y-
yCORRECTyANSWERS(Enzymeyhas)yactiveysite;yOnlyysubstrateyfitsy(theyactiveysite);
Describeytheyinducedyfitymodelyofyenzymeyaction.y[2]y-
yCORRECTyANSWERSActiveysitey/yenzymeynotycomplementary;yActiveysiteychangesy(sha
pe)y/yisyflexible;y(Changeyinyenzymeyallows)ysubstrateytoyfity/yE-Sycomplexytoyform;
Describeyoneywayythatytheylockyandykeyymodelyisydifferentyfromytheyinducedyfitymodel.y[1]y-
yCORRECTyANSWERSActiveysiteydoesynotychangey(shape)y/yisyfixedy(shape)y/yisyrigidy/ydo
esynotywrapyaroundysubstratey/y(already)yfitsytheysubstratey/yisycomplementaryy(beforeybindi
ng);
ExplainywhyytheyrateyofyreactionyofyanyenzymeyisylowyawayyfromyitsyoptimumypH.y[3]y-
yCORRECTyANSWERS(changeyinypH)yleadsytoybreakingyofybondsyholdingytertiaryystructur
e/ychangesychargeyonyaminoyacids;yenzyme/protein/activeysiteylosesyshape/denatured;ysu
bstrateywillynotybindywith/fityactiveysite;yfewer/noyESycomplexesyformed;
,Ayproteinymoleculeycontainsy150yaminoyacids.yWhatyisytheytotalynumberyofypeptideybondsyin
ythisymolecule?y[1]y-yCORRECTyANSWERS149
Howydoyyouycalculateymagnification?y[1]y-
yCORRECTyANSWERSM=yIy(Image)/yAy(actualysize)
Describeytheywaysyinywhichyprokaryoticycellsyandyeukaryoticycellsydiffer.y[3]y-
yCORRECTyANSWERSProkaryoticycellsydoynotyhaveyaynucleusy/yhaveygeneticymaterialyiny
cytoplasm;yDNAyinyloopy/yring;yNotyassociatedywithyproteinsy/ydoynotyhaveychromosomesy/c
hromatiny/ydoynotydivideybyymitosis;ySmalleryribosomes;yNoymembrane-
boundyorganelles;ySuchyasymitochondriay/ylysosomesy/yendoplasmicyreticulumy/yGolgiy/ychl
oroplasts;yProkaryoticycellsymayyhaveymesosomes;yProkaryoticycellsysmaller;yMayybeyencl
osedybyycapsule;
Whatyisytheyfunctionyof:ya)Ribosomeyb)SmoothyERyc)Golgiyapparatusyd)yChloroplastye)Mit
ochondriay[5]y-
yCORRECTyANSWERSa)Proteinysynthesisyb)Lipidysynthesisyandytransportyc)Processingy
andypackagingyproteinsyforysecretionyd)Photosynthesisye)AerobicyrespirationytoyproduceyA
TP
Explainytheyadvantagesyandylimitationsyofyusingyaytransmissionyelectronymicroscopey[5]y-
yCORRECTyANSWERSAdvantages: ySmallyobjectsycanybeyseen;yTEMyhasyhighyresolutiony
asywavelengthyofyelectronsyshorter;yLimitations:yCannotylookyatylivingycellsyasycellsymustybe
yinyayvacuum;ymustycutysectiony/ythinyspecimen;yPreparationymayycreateyartefact;yDoesynoty
producey3Dyorycoloredyimage;
Whyyanyelectronymicroscopeycanybeyusedytoyproduceyimagesy[2]y-
yCORRECTyANSWERSEMygivesyhighyresolutionydueytoyshortywavelengthyofyelectrons;
Explainyhowyvirusesycauseydamageytoycells.y[3]y-
yCORRECTyANSWERSusesy/ybreaksyupy/ydigestsyhostynucleary/ygeneticymaterialy(allowyref
erencesymadeytoyDNAy/RNAyinsteadyofynucleary/genetic);yvirusyDNAy/ygeneticymaterialyinse
rtedyintoyhostsyDNAy/ychromosomey/ygeneticymaterial;yhostycellsyaminoyacidsyareyusedytoysy
nthesizeyviralyproteins;ycellylysis;ybyyenzymey(producedybyyexpressingyayvirusygene);ytoxiny
production;
Describeyandyexplainyhowycellyfractionationyandyultracentrifugationycanybeyusedytoyisolatey
mitochondriayfromyaysuspensionyofyanimalycells.y[5]y-
yCORRECTyANSWERSCellyhomogenisationytoybreakyopenycells;y1.yAcceptysuitableymeth
odyofybreakingyopenycells.yFilterytoyremovey(large)ydebrisy/ywholeycells;y2.yRejectyremovesyc
ellywalls.yUseyisotonicysolutionytoypreventydamageytoymitochondriay/yorganelles;yKeepycoldyt
oypreventy/yreduceydamageybyyenzymesy/yuseybufferytoypreventyproteiny/yenzymeydenaturati
on;yCentrifugey(atyloweryspeedy/y1000yg)ytoyseparateynucleiy/ycellyfragmentsy/yheavyyorganel
les;yRe-
spiny(supernatanty/yafterynucleiy/ypelletyremoved)yatyhigheryspeedytoygetymitochondriayinypell
ety/yatybottom.
Nameytwoystructuresypresentyinyeukaryoticycellsythatyareynotypresentyinytheycellsyofyprokary
otes.y[2]y-
yCORRECTyANSWERSNucleus;ymitochondria;ychloroplast,yGolgi,yRER;ySER;ycentrioles
Describeytheyfluid-mosaicystructureyofyaycellysurfaceymembrane.(5/8ymarks)y-
yCORRECTyANSWERSPhospholipids yandyproteins;yPhospholipidybilayer;yArrangementyof
yphospholipidymoleculesy'Tailsytoytails';'Floating'(protein)ymoleculesy/ymoleculesycanymovey
inymembrane;Intrinsicyproteinsyextendythroughybilayer;yExtrinsicyproteinsyinyouterylayeryonl
, y;(Ref.ytoyintrinsicyandyextrinsic,yunqualified,ygainsy1ymark);Detailyofychannelyproteinsy/yprot
einyshapesy/yglycoproteins;Presenceyofycholesterolybetweenyphospholipids.
Describeytheypartyplayedybyycellysurfaceymembranesyinyregulatingytheymovementyofysubsta
ncesyintoyandyoutyofycells.(6/10ymarks)y-yCORRECTyANSWERS1.yNon-
polar/lipidysolubleymoleculesymoveythroughyphospholipidylayer/bilayer;2.ySmallymolecules/
water/gasesymoveythroughyphospholipidylayer/bilayer;3.yIons/waterysolubleysubstancesym
oveythroughychannelsyinyproteins;4.ySomeyproteinsyareygated;5.yReferenceytoydiffusion;6.C
arriersyidentifiedyasyproteins;7.yCarriersyassociatedywithyfacilitatedydiffusion;8.yCarriersyass
ociatedywithyactiveytransport/transportywithyATP/pumps;9.yDifferentycellsyhaveydifferentypro
teins;10.yCorrectyreferenceytoycytosis;
Describeytheyroleyofytheyenzymesyofytheydigestiveysystemyinytheycompleteybreakdownyofysta
rch.y(6ymarks)y-
yCORRECTyANSWERS1.yAmylase;2.y(Starch)ytoymaltose:3.yMaltase;4.yMaltoseytoyglucos
e;5.yHydrolysis;6.y(Of)yglycosidicybond;
Explainyhowytheysmallyintestineyisyadaptedytoyitsyfunctionyinytheyabsorptionyofytheyproductsy
ofydigestion.y(6/9ymarks)y1.y-
yCORRECTyANSWERSLargeysurfaceyareayprovidedybyyvilliy/ymicrovilli;2.ylongy/yfoldsyincre
aseysurfaceyareay/ytimeyforyabsorption;3.ythinyepithelium;4.yshortydiffusionypathway;5.ycapill
aryynetworkyabsorbsyaminoyacidsy/ysugars;6.ylactealyforyabsorptionyofydigestedyfats;7.yMain
tainsyaysteepyconcentrationygradient;8.ymitochondriaysupplyyATPy/yenergyyforyactiveytransp
ort;9.ycarrieryproteinsy(inymembranes);
Describeyandyexplainytheyroleyofydiffusionyinytheyabsorptionyofydigestedyfoodybyytheyileum.y(
4ymarks)y-
yCORRECTyANSWERS1.ymovementyalongy/ydownyconcentrationygradient;2.ymonoglyceri
desy/ymicelles/fattyyacidsymoveyintoyepithelialycells;3.ymonoglyceridesymoveyfromyepitheliu
myintoyblood;4.ychylomicronsymoveyintoylactealsy/ylymph;
Describeyandyexplainytheyroleyofyfacilitatedydiffusionyinytheyabsorptionyofydigestedyfoodybyyt
heyileum.y(3ymarks)y-
yCORRECTyANSWERS1.ymovementyalongy/ydownyconcentrationygradient;2.yreferenceytoy
carriery/ychannelyproteins;3.ymonosaccharidesyorynamedy/yaminoyacidsymoveyintoyepithelial
ycells;
Describeyandyexplainytheyroleyactiveytransportyinytheyabsorptionyofydigestedyfoodybyytheyileu
m.(4/6ymarks)y-
yCORRECTyANSWERS1.ymovementyagainstyconcentrationygradient;2.yenergyy/yATPyrequ
ired;3.yreferenceytoycarrieryproteins;4.ymonosaccharidesyorynamedy/yaminoyacidsymovedyin
toyepithelialycells;5.yreferenceytoyco-
diffusionye.g.yglucoseyandyNaCl;6.ymonosaccharidesyorynamedy/yaminoyacidsymoveyintoybl
ood
DescribeyhowytheystructureyofyDNAyisyrelatedytoyitsyfunctiony(4/7marks)y-
yCORRECTyANSWERS1.ySugar-
phosphateybackbone:yprovidesystabilityy&yprotectsybasesy2.yDoubleystranded:yreplicationyc
anyoccurysemi-
conservativelyywhereyeachystrandycanyactyasytemplateymakingyreplicationymoreyaccuratey3
.yComplementaryybaseypairingy(A-TyandyG-
C)ymakesyreplicationymoreyaccuratey4.yIndividualyhydrogenybondsyareyweak:yeasilyyunzipy
