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BIO-251 FINAL EXAM QUIZ QUESTIONS WITH COMPLETE SOLUTIONS
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BIO-251 FINAL EXAM QUIZ QUESTIONS WITH COMPLETE SOLUTIONS
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BIO-251 FINAL EXAM QUIZ QUESTIONSWITH COMPLETE SOLUTIONS
1)aActinaisaoneaofatheamostaevolutionarilyaconservedaproteins.aWhatadoesathisatellayouaabou
tatheastructureaandafunctionaofathisaproteinainaeukaryoticacells?a-
acorrectaanswera✔✔Evolutionarilyaconserved-
hasn'taundergoneamuchachangeasinceaexistenceaofaeukaryotes.
Tellsausathatathisaproteinaisavitalaforacellularafunction.aTellsausaitacanadoaaavarietyaofafunctions
ainacells.
Itsasoaconservedabecauseaitaisaveryaimportantaforacells.aMultifunctionalamakesaitamoreawell-
conservedabecauseamonomersathatamakeait.aUpaareaveryasimple,aandaareaableatoacombinea
in.aaacomplexawayatoaperformaitsamanyafunctions.aItahasatoabeasomethingatoadoawithatheafacta
thatasoamanyaotheraproteinsacanabindatoait.aG-
actinahasalotsaofaaaasideachainsathatastickaout.aSequenceaofaaaasideachainsamakeaitamultifun
ctional.aEveryadifferentaproteinathatabindsatoaactinahasatoabindatoaaaspecificaplaceaonaactin.a
Mutationainaaaasideachainsacouldanegativelyaimpactatheabinding.
1)aIamentionedaphalloidinaisaaatoxicaproducedabyatheadeathcapamushroom.aItaisatoxicabecau
seaitabindsaacrossatwoaactinamonomersaandaholdsathematogether.aInacontrast,alatrunculin,aa
notheratoxina-athisaoneaisamadeainaspongesa-atightlyabindsatoaG-
actinamonomers.aDescribeatheaeffectaeachadrugawouldahaveaonaactinatreadmilling.a-
acorrectaanswera✔✔Phalloidin-
filamentsawillacontinueatoaelongate,aunableatoatakeafilamentsaoffaofachain.aPreventsadepoly
merization.aPolymerizationawouldastopaforathisawhenatheacellareachesabelowasomeathreshol
daofafreeaG-actin.
Latrunculin-awouldabind.aTo.aG-
actin,apreventapolymerization,astopaforceaagainstaPM,alengthaof.aF-
actinawouldagetashorterabecauseathereawouldabeadepolymerizationabutanotapolymerization.a
Levelaofamonomersainacellamayamakeadepolymerizationaslowadown
1)aLet'sathinkaaboutatheastagesaofadeath.aIfayouawereaaacrimeasceneainvestigatoraandayouaw
ereaexaminingaaabodyaataambientatemperature,ayou'daprobablyaknowatheafollowing:
Ifatheabodyafeelsawarmaandanoarigoraisapresent,adeathaoccurredaundera3ahoursabefore.
Ifatheabodyafeelsawarmaandastiff,adeathaoccurreda3-8ahoursaearlier.
Ifatheabodyafeelsacoldaandastiff,adeathaoccurreda8-36ahoursaearlier.
Ifatheabodyaisacoldaandanotastiff,adeathaoccurredamoreathana36ahoursaearlier.
Rigorarefersatoarigoramortis,awhichaisatheastiffeningaofaaabodyaafteraitadies.aKnowingawhatayo
uaknowaaboutacellulararespirationaandamyosin'saATPaseacycleaandamuscleafunction,aplease
aansweratheafollowingaquestions:aWhataisatheabasisaofarigoramortis?aWhyaisaitareferredatoaasa
stiffeningaandanotacontracting?aWhyadoesaitatakea3ahoursaforastiffeningatoaoccur?aWhyadoes
,athearigoraretreat?a-acorrectaanswera✔✔Basisaofarigoramortis-
aafteraATPahydrolyzed,aandaafteraeverythingaelseatakesaplace,aATPastops.aInadeath,aATParu
nsaout,acausesamusclesatoabeastiffabecauseanoaATPatoareleaseamyosinaheadafromaactin.
Stiffeningainsteadaofacontracting-
myosinaisanotamovingaactinafilamentsaalong,amyosinais.aBoundatoaactinaandaisaimmovable.a
Noacycleaofacontraction,asoawillaonlyabeastiff
Whya3ahours-thereawillastillabeasomeaATPaleftaoverawhichawillabeausedaupauntilaitaisagone.
Whyadoesarigorafinallyagoaaway?-
atheabodyabeginsatoadecayasoatheaproteinsawillabeadegraded,areleasingatheamyosinafromathea
actin.aactinafibersafallaapart,amyosinaheadsadegrade,abecomesapliableaagain
1)aYouaknowathatacanceracellamigrationaisaaakeyapartaofametastasis,awhichaisatheadeadliestaa
spectaofacancer.aSo,ayouawantatoadevelopaaadrugathatacanainhibitacanceracellamigration.aYou
aknowathatamyosin-2-
basedacontractionaisarequiredaforacellamigrationaandasoayouaspecificallyawantatoadevelopaaad
rugatoainhibitait,amyosin-2.a(Note:atheamyosin-
2athatapromotesamigrationaisaveryasimilaratoabutaultimatelyaaadifferentaisoformafromamusclea
myosin-2.aTheanon-muscleamyosin-
2aformsasmallerafilamentsathataareamoreadynamic,awhereasatheamyosin-
2athickafilamentsainamusclesaareaveryastableaandalargerastructures.)
a)aWhataaspectaofamigrationaisamyosin-
2ainvolvedain.aThinkaaboutatheastepsaofamigrationadiscussedainalecturea(andaseeafigurea17-
33ainayouratext).aWhereaisatheaforceabeingaproducedathatainvolvesamyosin-2?a-
acorrectaanswera✔✔Myosin-
2aisainvolvedainaretractiona(backaendaofacell).aForceabeingaproducedaisawhereaactinabringsau
paendaofacellabackaintoamiddle
a)aYouadevelopaaadrugathataseemsatoainhibitamyosin-
2,abutayouaareaunsureaofaitsamechanismaofaaction.aInageneral,ahowamightayouaknowawhethe
ratheadrugablocksaATPafromabindingatoamyosinaversusaallowingaATPatoabindabutablockingahy
drolysis?aCanayouathinkaofaaawayatoatestathisainaaabiochemicalaassayawithapurifiedaactinaanda
myosin-2?a-
acorrectaanswera✔✔YouacouldatrackatheaamountaofafreeaATP,aifathereawasaaacomparativelyal
owaamtaitawouldabeabindingaandaifathereawasaaahighaamount,aitawouldn'tabe.aIfaATPacannotabi
nd,ayoudahaveatheasameaamountaofaATPainayourasolutionaasayouastartedawith.aControl-
withoutadrug
Youracontrol,atheaATPawouldadecreaseaafteragoingathroughatheacycle
Experimental-ATPalevelsawouldastayahigheraifaATPabindingawasapreventedabyatheadrug.
Ifayouacarriedaoutatheasameaexperiment,acouldayouatellawhetheraitawasaableatoabindabutanotaa
bleatoahydrolyze?aNo-
aATPalevelsawouldastayatheasameaasacomparedatoawhenayouafirstaputaitain.adependsaonaratioa
concentrationaofaATPatoaactinaandamyosin.
, Anotheraexperiment-agenerateamichaelisamentenacurve-
keepamyosinalevelsatheasame,achangealevelsaofaATP,aseeaifadrugacompetitivelyainhibitsait.aK
davalueawouldaincreaseaifaitaaffectedaATPabinding.aButacannotaanalyzeawhetheraatpawasabo
undaoranotatoamyosin
a)aAfterathinkingamoreaaboutathis,ayouadecideathatagivingaaapersonaaapillathatainhibitsamyosin
-
2amightanotabeaaagoodaidea,aevenaifaitadoesastopatumoracellametastasisareallyawell.aWhyaisath
at?a-
acorrectaanswera✔✔Notaaagoodaideaabecauseaitawouldaaffectahealthyacellsaasawellaasacance
racells.aWouldacauseaaalotaofaissuesaforatheaperson,aincludingamuscleacontractionaandacella
motility;adrugasoundsalikeatheadeathacapamushroomatoxins.
1)aMicrotubulesacanabeaformedainavitroafromatubulinathataisaboundatoaGTPaanaloguesathata(u
nlikeaGTP)acannotabeahydrolyzed.aWhatapropertiesawouldayouaexpectatheseamicrotubulesat
oapossess?aCouldasuchamicrotubulesastillashowadynamicainstability?a-
acorrectaanswera✔✔TheseaMTsawouldapolymerizeabutanotadepolymerize,asoathereawouldab
eanoneaoralessadynamicainstability.aGTPacapastabilizesatheaendsaofathe.aMTSaandahydrolyze
saafteraaalittleawhile.aTheseaMTsawouldanotashowadynamicainstabilityabecauseatheyawouldn't
abeadepolymerizing,aonlyapolymerizing—exceptionallyastable
1)aIfaanaindividualakinesinamoleculeacanamoveaataaarateaofa800anm/secainaanainavitroamotilitya
assay,awhataisatheamaximalaturnoveraratea(ATPamoleculesahydrolyzedaperasecond)abyaonea
ofatheamolecule'samotoradomains.aWhatainformationadoayouaneedatoaanswerathis?aThinkaab
outahowatheakinesinsawalk.aNoteathataa-aandab-tubulinaareaeachaabouta4anmainalength.a-
acorrectaanswera✔✔8nm/step.a100asteps/sec.aATPmolecaperasecondawouldabea100/secafor
atwoadomains,asoa50/secaforaONEadomain.
1)aBecauseacytoplasmicavesiclesaareaseenatoamoveainabothadirectionsawithinatheaaxonaofaaa
neuron,acanayouaconcludeathatasomeamicrotubulesaareaorientedawithatheiraplusaendafacingat
heaaxonaterminusaandaothersaorientedawithatheaoppositeapolarity?aWhyaorawhyanot?a-
acorrectaanswera✔✔WeacannotaconcludeathisabecauseaMTsaonlyagrowaoutaofaoneaspotainath
eacell,aplusasideagrowsaoutwardabutavesiclesaareaallowedatoamoveabackaandaforthabecauseat
heyaareakinesinsaandadyneins
1)aHowadoesasignalingabyahydrophobicamoleculesalikeatheasteroidahormonesadifferafromasig
nalingabyahydrophilicamoleculesalikeapeptideahormones?a-
acorrectaanswera✔✔Hydrophobicamoleculesalikeasteroidahormonesahaveaintracellularasigna
lingareceptors-
hydrophobicaallowsaitatoadiffuseathroughamembrane.aAdditionally,asignalingapathwayaisadiff
erent.aPeptideasignalingapathwayatransducedabyabindingatoasomeacellamembraneareceptora
whicharequiresamoreaofaaasignalacascadeathanasteroidasignalingapathway.aSteroidahormone
sagoarightatoanucleusawhereareceptorais,aallowsasteroidatoagoaintoanucleus—
shorterapathway.aSpeedaofaresponseainacellasignalingacanatellausaaalot-
twoawaysaweathinkaofathis:abindingaofamolecatoareceptor-
cascadearesultsainaactivationaoradeactivationaofaproteinsaalreadyathere-
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