CEBIO1990AlexLamPaperIMarkingScheme&YearReportP.1.(a)(i)cellsAandD1or0possessionofcellwall,1andlarge/centralvacuole/peripheralnucleus1(1)cellAisforregulatingthesizeofthestomatalopening/providesapassageforgases/watervapour1cellBisfortransmittingnerveimpulses/message/information1(2)cellA-thickerinnerwallandthinnerwall/kidney-shaped1cellB-longcellularextension/nervefibre/branchedendings1(ii)cellCbursts/swells1cellDbecomesturgid/showsnochange1waterpotentialofdistilledwaterisgreaterthanthatofthecells(CandD)1waterentersthecellsbyosmosis1cellCexpandscontinuouslyuntilitbursts1butcellDdoesnotburstbecauseofthepresenceoftheinelasticcellwall1Total:13Marks1.(a)(i)&(ii)Mostcandidateswereabletoanswerthequestioncorrectlywithreferencetothefeaturesshowninthediagram.Asmallnumberofcandidates,however,includedfeaturesnotshowninthediagramsuchasthepresenceofchloroplastincellAormyelinsheathincellB.Thissuggeststheyhadansweredbyrotememory.Somecandidatesdidnotrealisethatvacuolesarepresentinbothplantandanimalcells,althoughthevacuolesinplantcellsareusuallylargerandcentralinposition.(iii)ManycandidatescouldgiveaclearandaccurateaccountofthechangesincellsCandDusingtheconceptofwaterpotential.Thisshowsthatwaterpotentialisausefulconceptinunderstandingandexplainingosmosisinlivingcells.1.(b)(i)from2.0sto4.0s1pressureinthelungsisgreaterthantheatmosphericpressure1(ii)-intercostalmusclesrelax)-tolowertheribs)-diaphragmrelaxes)anyTHREE1,1,1-tocurveupward)theseactionsdecreasethevolumeofthethorax/increasetheairpressureofthelungs1(iii)15breathsperminute(nounit,nomark)1(iv)showingahigherfrequency1showingagreatermagnitude1(nounit/referencepoint,nomark)Total:9Marks1.(b)(i)Quiteanumberofcandidatesstatedwronglythatairmovesoutofthelungswhenthepressureinthelungsisincreasing.Theyfailedtoseethatairisbreathedoutonlywhenthelungpressureexceedstheatmosphericpressur