ANSWERSCHEMEBIOLOGYPAPER2FORM4MIDYEAR1 (a) (i) P:Roughendoplasmicreticulum

Q:Golgibody11

2

(ii) RibosomeatPsynthesizesprotein ProteinthatissynthesizedistransportedbyPtoQ

Qmodifiestheproteintoenzymes//Qpackagestheenzyme/protein.

111

3

(b) (i)

11

2

(ii) Theonionepidermalcellshavecellwallwhilecheekcelldonothavecellwall.

1 1

(c) Thecelldoesnotdivide/differentiate Becausetherearenogenes(thatcontrolmitosis/differentiation)

11

2

(d) S(mitochondria):itgeneratesenergyMeristematiccellsrequiremoreenergytoundergomitosis/celldivision

11

2

TOTAL 122 (a) (i) Redbloodcell/erythrocyte 1 1 (ii) Transportoxygentobodycell 1 1 (b) (i)

2 2

(ii) P1Saltsolutionishypertonic

P2OsmosisoccursP3WaterfromerythrocytediffusesoutP4Erythrocyte(becomes)crenated/shrink.

1111

Any3

Max3

(c) (i) Phospholipidbilayer 1 1 (ii) Lipid/protein 1 1 (iii) P1Detergentdissolvesthelipidintheplasmamembrane.

P2Plasmamembranedisintegrates/destroyed.P3Cytoplasm(ofredbloodcell)mixintothesolutionP4CellPishaemolysed.

1111

Any3

Max3

Total 123 (a)

11

2

(b) Itisamembranethatallowsonlycertainsubstancestomovefreelyacrossitwhileotherscannot.

1 1

(c) FacilitateddiffusionSimplediffusion/osmosis

11

2

(d) (i) S1:Aminoacidbindstoaspecificsiteonthecarrierprotein.S2:Carrierproteinchangesitsshapeandreleasestheaminoacidontheotherside.S3:Themovementofaminoacidisdown/followstheconcentrationgradient.

111

2

(ii) P1:Fattyacid/glycerol/vitaminA/D/E/K,steroidsS1:Small,nonpolarE1:Theyarelipidsoluble/canmovethroughthephospholipidbilayer.P2:Water,carbondioxideandoxygen.S2:small,unchargedmoleculesE2:Theyarelipidsoluble/canmovethroughthephospholipidbilayer.

111111

3

(e) P:Theadditionofpreservativessuchasconcentratedsalt/sugarsolutionmakesthesurroundingsolutionhypertonictothecellsapofthecucumber.S1:CausingwatertodiffuseoutfromthecucumbercellsbyosmosisS2:ThedehydratedconditionofthecucumberpreventthegrowthofbacteriaandfungiS3:causeswatertodiffuseoutofthebacteria/fungiS4:Bacteria/fungidehydratesanddies

11111

3

TOTAL 134 (a) X:Ribosome

Y:Golgiapparatus11

2

(b) (i) Pancreas//Ileum//stomachepithelialcell//salivarycell 1 1 (ii) F:Theproductionofextracellularenzymeisincomplete/

disrupted/affected.E1:(withoutGolgiapparatus/Y),theproteincannotbemodifiedintoextracellularenzyme.E2:Proteincannotbesorted.E3:Extracellularenzymecannotbereleased/transportedtothetargetedcell/organ.Any2

1111

3

(c) E1:Hightemperaturealter/changethe(threedimensional)shapeoftheactivesiteofenzymemolecules.E2:substratesthuscannolongerfitintotheactivesitesoftheenzyme.E3:thereactioncannotbecarriedout//substratecannotbehydrolysed.

111

2

(d) E1:Bloodismadeupofprotein.E2:Proteinisbrokendown/digestedbyprotease(enzyme)E3:Therefore,theuseofamylase(enzyme)inthedetergentpowderwouldnotbeeffective.Any2

111

2

(e) E1:GallstonesblockedthesecretionofbileE2:LipidscannotbeemulsifiedE3:Therateoflipasereactionwillbecomeslower//digestionoflipidswillbedisrupted/isincomplete.E4:Thepatientmightfaceobesity//becomeobese.Any3E

1111

3

TOTAL 13

5 (a) Glucose 1 1

(b) P1:EnzymearehighlyspecificP2:EnzymearenotdestroyedattheendofreactionP3:Enzymecatalysedreactionarereversible

111

Max2

(c) (i) P1:60CishightemperatureP2:Atveryhightemperaturethechemicalbondthathold

enzymesmoleculestogetherbegintobreakP3:thusalteringthethreedimensionalshapeofenzymeP4:destroyingactivesiteofenzyme/enzymedenatured

1111

Max3

(ii) P1:AtlowpHvalueexcesshydrogenionsattachtotheactivesiteofenzyme

P2:CauseionicchargesontheactivitysitetobealteredP3:Substrateisunabletobindtotheenzyme/reaction

cannottakeplace

111

Max2

(d) (i) P1:LipaseE1:RipeningcheeseOrP2:RenninE2:Solidifymilkprotein

1111

Max2

(ii) P1:CelluloseE1:Breakdowncelluloseandremovesseedcoatfromcereal

grains

11

2

TOTAL 126 (a) (i) PEnzymesarebiologicalcatalyststhatspeedupbiochemical

reactionsinthecell.2

2

(ii) P1 Enzymes are proteins which are synthesised by living organisms

P2 Enzymes alter or speed up the rates or chemical reactions but remainunchangedattheendofreactions.

P3 Enzymes have specific sites called active sites to bind to specificsubstrates.

P4 Enzymes are highly specific each enzyme can only catalyse onekindofsubstrate.

P5 Enzymes are needed in small quantities because they are notusedupbutreleasedattheendofareaction.

111111

8

P6 Enzyme can catalyse specific reactions both in the forward and in the reverse directions. Most enzymecatalysed reactions arereversible.P7 Many enzymes require helper molecules, called cofactors, to

functionP8 Enzyme activities can be slowed down or completely

stoppedbyinhibitors(heavymetalssuchasleadandmercury)

11

(b).P1Enzymesaresynthesisedbyspecificcells.2.P2Enzymeswhichareproducedandretainedinthecellfortheuse

ofthecellitselfarecalledintracellularenzymes.3.P3Enzymeswhichareproducedinthecellbutsecretedfromthecell

tofunctionexternallyarecalledextracellularenzymes.a.P4ThenucleuscontainsDNAwhichcarriestheinformationforthe

synthesisofenzymes.b.P5Proteinthataresynthesisedattheribosomesaretransported

throughthespacewithintheroughendoplasmicreticulum(roughER).c.P6ProteinsdepartfromtheroughERwrappedinvesiclesthatbud

offfromthemembranesoftheroughER.d.P7Thesetransportvesiclesthenfusewiththemembraneofthe

Golgiapparatusandemptytheircontentsintothemembranousspace.e.P8Theproteinsarefurthermodifiedduringtheirtransportinthe

Golgiapparatus,forexample,carbohydratesareaddedtoproteintomakeglycoproteins.

f.P9SecretoryvesiclescontainingthesemodifiedproteinsbudofffromtheGolgiapparatusandtraveltotheplasmamembrane.

g.P10Thesevesicleswillthenfusewiththeplasmamembranebeforereleasingtheproteinoutsidethecellasenzymes.

1111111111

10

TOTAL 207 (a) (i) X:Musclecell

Y:NervecellZ:Redbloodcell

111

3

(ii) X:causemovementY:transmitnerveimpulsesZ:transportsoxygenfromthelungstothecellsofthebody

111

3

(b) CelleachcellcarriesoutaspecificfunctionagroupofcellsthathavethesamefunctionandthesamestructureformatissueTissuemusculartissuewhichisformedfrommusclecellsisableto

112

contractandrelaxtoproducemotionnervoustissueconsistsofneuronesandisspecialisedfortransmittingnerveimpulsesconnectivetissue(blood)transportsmaterialsthetypesoftissuesdescribedabovefunctiontogethertoformanorgan(heart)Organtheheartfunctionstopumpbloodtoallpartsofthebodybloodvesselstransportoxygentheheartandbloodvesselsworktogethertoformthecirculatorysystem(organsystem)Organcellsthefunctionofthecirculatorysystemistotransportmaterialssuchasnutrients,gasesandmetabolicwastesaroundthebody.thecirculatorysystemandotherorgansystemsworktogethertoformamulticellularorganism.

22111111

14

TOTAL 208 (a) Totransportoxygentotheotherpartsofbody 1 1 (b) (i)P1thesolutionishypertonictotheredbloodcell

P2OsmosisoccurP3WatermoleculediffusesinthecellsP4thecellstarttoswellandeventuallyburstP5Haemolysisoccur

(ii)P1thesolutionoutsidethecellisisotonictothecellsap

P2WaterdiffuseinandoutthecellatequalrateP3thecellmaintainitsshape/notchange

P4noredbloodcellshrinks/burst (iii)P1Thesolutionishypertonictotheredbloodcell

P2WatermoleculediffusesoutofthecellsbyosmosisP3creanationoccurs

Any3

Any3

3

9

(c) (i)F1Thiscellularcomponent/plasmamembraneispushedagainstthecellwallF2Thedistilledwater/solutionishypotonictothecellsapE1Distilledwaterishypotonictothecellsap//cellsaphypertonictodistilledwaterE2WatermoleculediffusesintothecellbyosmosisE3VacuoleExpand/swellupE4thecellarehighlyturgid

Any4

(ii)P1thesolutionoutsidethecellisisotonictothecellsapP2WaterdiffuseinandoutthecellatequalrateP3thecellmaintainitsshape/notchange

P4noplantcellshrinks(iii)P1Thesolutionishypertonictocellsap

P2WatermoleculediffusesoutofthelargecentralvacuolebyosmosisP3theplasmamembranepullawayfromthecellwall

P4Plantcellbecomeflaccid

Any2

Any3

9

(d) Plantcellarenotburstwhenimmersedinhypotonicsolutionbecauseithaveacellwallwhileredbloodcelldoesnothaveit.

1

TOTAL 209 (a) P1Waterisimportantforlifebecauseitschemicalandphysical

propertiesallowittosustainlife.P2Waterisapolarmoleculewhichconsistsof2hydrogenatomsand1oxygenatom.P3Apolarmoleculeisamoleculewithanunequaldistributionofcharges.Eachmoleculehasapositivelychargedandanegativelychargedend.Polarmoleculesattractoneanotheraswellasions.Becauseofthisproperty,waterisconsideredthesolventoflife.P4ItisthetransportmediuminthebloodP5Itactsasamediumforbiochemicalreactions.P6Waterhelpsinthemaintenanceofastableinternalenvironmentwithinalivingorganism.P7Theconcentrationofwaterandinorganicsaltsthatdissolveinwaterisimportantinmaintainingtheosmoticbalancebetweenthebloodandinterstitialfluid.P8Ithelpsinlubrication.P9Watermoleculeshaveveryhighcohesion.Watermoleculestendtosticktoeachotherandmoveinlongunbrokencolumnsthroughthevasculartissuesinplants.

111111111

Any8

(b) P1DNAandRNAaresynthesizedincellsbyDNApolymerasesandRNApolymerases.P2Shortfragmentsofnucleicacidsalsoarecommonlyproducedwithoutenzymesbyoligonucleotidesynthesizers.P3Theprocessinvolvesformingphosphodiesterbondsbetweenthe3'carbonofonenucleotideandthe5'carbonofanothernucleotide.P4Akeyfeatureofallnucleicacidsisthattheyhavetwo

1111

distinctiveends:the5'(5prime)and3'(3prime)ends.Thisterminologyreferstothe5'and3'carbonsonthesugar.P5ForbothDNA(shownabove)andRNA,the5'endbearsaphosphate,andthe3'endahydroxylgroup.P6AnotherimportantconceptinnucleicacidstructureisthatDNAandRNApolymerasesaddnucleotidestothe3'endofthepreviouslyincorporatedbase.P7Anotherwaytoputthisisthatnucleicacidsaresynthesizedina5'to3'direction.P8MostDNAexistsinthefamousformofadoublehelix,inwhichtwolinearstrandsofDNAarewoundaroundoneanother.P9Themajorforcepromotingformationofthishelixiscomplementarybasepairing

P10ThetwostrandsofDNAarearrangedantiparalleltooneanother:viewedfromlefttorightthe"top"strandisaligned5'to3',whilethe"bottom"strandisaligned3'to5'.

P11GCbasepairshave3hydrogenbonds,whereasATbasepairshave2hydrogenbonds:oneconsequenceofthisdisparityisthatittakesmoreenergy(e.g.ahighertemperature)todisruptGCrichDNAthanATrichDNA

1111111

Any10

(c) P1functioninencoding,transmittingandexpressinggeneticinformationinotherwords,informationisconveyedthroughthenucleicacidsequence,ortheorderofnucleotideswithinaDNAorRNAmolecule.

P2Stringsofnucleotidesstrungtogetherinaspecificsequencearethemechanismforstoringandtransmittinghereditary,orgeneticinformationviaproteinsynthesis.

11

2

TOTAL 20