AQA A-level Biology paper 1

AQA A-level Biology paper 1
questions and correct answers



largemoleculesoftencontaincarbon.why?-CORRECTANSWERS-
theycanreadilyformbondswithothercarbonatoms.thisformsa'backbone'.otheratomscanthena
ttach.



describebenedictstestforreducingsugars-CORRECTANSWERS-
addequalvolumesofthesugarsampleandbenedictsreagent.

heatthemixtureinawaterbathfor5minutes.

brickredprecipitatewillform.



whatisareducingsugar?-CORRECTANSWERS-
asugarthatcanreduce(giveelectronsto)anotherchemical.



describethebenedictstestfornonreducingsugars-CORRECTANSWERS-
withfoodsample,addanequalvolumeofdilutehydrochloricacidinatesttube.

placetesttubeinwaterbathfor5mins.

addsodiumhydrogencarbonatesolution.

heatresultingsolutionwithanequalvolumeofbenedicts.solutionfor5minutes.

turnsorange/brown.



whatdoesdilutehydrochloricaciddointhebenedictstestfornonreducingsugars?-
CORRECTANSWERS-
ithydrolysesanydisaccharideintomonosaccharides,thusalsoformingreducingsugars.

,describethestructureofstarch-CORRECTANSWERS-chainsofalphaglucose

somechainsarebranched=amylopetcin

somechainsarecoiled=amylose



whatpurposedoesthestructureofamyloseserve?-CORRECTANSWERS-
makesthemoleculecompactsoitisstoredmoreeasily.



whatpurposedoesthestructureofamylopectinserve?-CORRECTANSWERS-
moresurfaceareaforenzymestoworkon,thusglucosemoleculescanbereleasedatamuchquickerr
ate.



howisthestructureofstarchsuitedtoitsfunction?-CORRECTANSWERS-
1.starchisinsolubesoitdoesntaffectwaterpotential

2.itislargeenoughthatitdoesntdiffuseoutofcells

3.compactenoughsothatalotofitcanbestoredinasmallspace

4.branched=eachendcansimultaneouslybeactedonbyenzymes,soglucoseisquicklyreleased



howisthestructureofglycogensuitedtoitsfunction?-CORRECTANSWERS-
1.insoluble,sonoeffectonwaterpotentialofcell

2.insoluble,sodoesntdiffuseoutofcells

3.compact,alotofitcanbestoredinasmallspace

4.veryhighlybranched=eachendcansimultaneouslybeactedonbyenzymes,soglucoseisquicklyre
leased



whydoanimalsneedhighlybranchedglycogen?-CORRECTANSWERS-
becauseanimalsmetabolicrateisfasterthanplantsandsoneedsglucosetobereleasedquicker.



describethestructureofcellulose-CORRECTANSWERS-madeupofstraightchainsofbetaglucose

thechainsareparalleltoeachother,soHbondsformcross-linkages

alltheHbondstogetherstrengthensthecellulose

, formsmicrofibrils



drawalphaandbetaglucose-CORRECTANSWERS-



howdoesthestructureoftriglyceridesrelatetotheirproperties?-CORRECTANSWERS-
1.triglycerideshaveahighratioofenergy-storingcarbon-
hydrogenbondstocarbonatoms,soitsagoodsourceofenergy.

2.lowmasstoenergyratio,sotheyregoodenergystoragemolecules.

3.largeandnon-polar,thereforeinsoluble,thereforedon'taffectosmosis.

4.highratioofhydrogentooxygenatoms,socanreleasewaterwhenoxidised,henceprovideasourc
eofwater



whataretherolesoflipids?-CORRECTANSWERS-1.sourceofenergy

2.waterproofing

3.insulation

4.protection



howdoesthestructureofphospholipidsrelatetotheirproperties?-CORRECTANSWERS-
1.polar,thereforewillpositionitselftoformabilayer

2.thestructureallowsthemtoformglycolipidsbycombiningwithcarbohydrateswithinthecell-
surfacemembrane.theseareimportantincellrecognition.



drawthestructureofanaminoacid-CORRECTANSWERS-



drawhowadipeptideforms-CORRECTANSWERS-



whatismeantby'primarysequence'ofaprotein-CORRECTANSWERS-
Theuniquesequenceofaminoacidsthatmakeupaproteinorpolypeptidechain