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FinalExam Bio320 Dr.Chan

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FinalExamMultipleChoiceQuestions.2pointseach,answerall. 1)Theoverallchargeofaproteinisbasedon: A)Rgroup B)AminoGroup C)CarboxyGroup D)Acombinationoffactorsnotdiscussedinclass E)Proteinsarenotcharged 2)Thefoldingofaproteiniscontrolledbyits A)PrimarySequence B)SecondaryStructure C)TertiaryStructure D)QuaternaryStructure E)Randomfolding 3)WhichofthefollowingaboutPhosphatasesisTRUE A)PhosphatasesmakeATPfromADP B)Phosphatasescanturntheactivityofproteinsoff C)Phosphatasesaddphosphatefromproteins D)Phosphatasesremovethephosphateheadgroupfromphospholipids E)Allarefalse E)massofprotein

4)Whatisthepurposeofusingsecondaryantibodiesinfluorescentmicroscopy? A)aprimaryantibodycanonlylinktoatargetprotein,itcannothavea florescent tagappliedANDlinktothetargetprotein B)increasestheresolution C)increasesthemagnification D)thefurtherthetagisfromthetarget,thebetter E)amplificationofsignal 5)Electronmicroscopeshavebetterresolvingpowerthanlightmicroscopes because

A)Electronsaresmaller,sotheycanpassthruobjectsbetterthanlight B)Youdontneedtousefancylensestoincreasemagnification C)Electronshaveashorterwavelength D)Electronsscatterbetter E)Usinggoldparticleswithelectronshelpsthedetectorpickupsmaller objectsthatcannotbeobservedusinglightorafluorescenttag

6)WhatisamajordifferencebetweenHSP60andHSP70? A)HSP60ismonomericwhileHSP70ismultimeric B)HSP60isinvolvedinproteindegradationwhileHSP70is Involvedwithproteinfolding C)HSP60requiresphosphorlyatedmisfoldedproteinswhileHSP70does not D)HSP60has2foldingchamberswhileHSP70doesnot E)HSP60usesGTPwhileHSP70usesATP 7)InhibitionofE1couldresultin A)loweredproteinactivity B)increaseinproteinsynthesis C)aggregationofproteins D)accumulationofphosphorylatedproteins E)increaseofmonoubiquinatedproteins 8)Integralmembraneproteins A)Canspanaplasmamembrane B)Canbindmembranesviacovalentbondswithafattyacidtail C)Maybedisassociatedfromthemembranewithhighsaltbuffers D)Areonlyfoundontheplasmamembrane E)Maybedisassociatedfromthemembranewithbufferscontaining detergents 9)InactiveSar1isboundtoacofactor,whatisit A)Clathrin B)GTP C)GDP

D)COPII E)Sec13/31 10)Sar1GEFisresponsiblefor A)RemovingGDPfromSar1 B)AddingGTPtoSar1 C)BothAandB D)AddingClathrintoSar1 E)BindingthecargoreceptortoSar1 11)SOLUBLEERresidentproteinsthatareessentialforactivityhaveasequence onthemthatallowsthemtobereturnedtotheER.Thesequenceis: A)WKRP B)Bip C)KDEL D)aHydrophobicregionontheNterminalend E)Theycannotbereturned,theseenzymeswilljustbedegradedinthe E1/E2/E3 pathway

12)WhatistheMAINpurposeofthetransGolginetwork? A)Degrademisfoldedproteins B)Phosphorylateproteins C)Helpfoldproteins D)Sortproteins E)ReturnSolubleERproteinstotheER 13)AproteinisbeingprocessedbytheGolginetwork.Duringsorting,nosignal wasaddedtothisprotein.Theproteinwill: A)bedegradedinthelysosome B)itisalysosomeenzyme,soitgoestheretofunction C)Itispartofthesecretorypathwayandreleasedoutsideofthecell D)Itispackagedintosecondaryvesiclestobereleasedwhenneeded E)Itisreturnedtothecisgolgisidetobeprocessedoncemore 14)TheenzymesglucosidaseIandglucosidaseIIarefound: A)Cytosol B)ERLumen C)GolgiLumen D)Lysosome E)medialcisterna

15) Which of the following statements about Ran is CORRECT? a) Ran can bind to GTP but not to GDP. b) Ran can convert GDP to GTP by phosphorylation of GDP. c) Ran can bind to the nuclear export signal on a protein. d) Ran can diffuse across the nuclear pore. e) Ran is an important component of the nuclear envelope. 16)TheNuclearLocalizationSequence(NLS)is a)MadeupofbasicaminoacidsontheNterminalendoftheprotein b)MadeupofbasicaminoacidsontheCterminalendoftheprotein c)Madeupofhydrophilicaminoacidsanywhereonthesurfaceoftheprotein d)Madeupofbasicaminoacidsanywhereonthesurfaceoftheprotein e)MadeupofLeucinerichaminoacidsanywhereonthesurfaceofthe protein 17)F1ATPSynthasecanbindtoallofthefollowingionsormoleculesexcept: a)Protons b)NADH+ c)ADP d)ATP e)Phosphate

18)SERBPassociateswith_________atthe__________portionoftheprotein. a)S1PNterminal b)InsigWDrepeat c)SCAPWDrepeat d)SCAPNterminal e)InsigCterminal 19)InANIMALS,whatistheMicrotubuleOrganizingCenterofthecell? a)Centrosome b)GammaTuRC c)The+endofthemicrotubule d)Chromosomes e)NowelldefinedMTOCinAnimalCells. 20)Polymerizationofmicrofilamentsis

a)Dependentonthelengthofthemicrofilament b)DependentontheconcentrationoffreeActinADP c)DependentontheconcentrationoffreeActinATP d)DependentontheconcentrationoffreeActinGTP e)DependentontheconcentrationoffreeActinGDP

21)AtlowCa+2levels a)TroponinCunblocksthemyosinbindingsiteonmicrofilaments b)TroponinCblocksthemyosinbindingsiteonmicrofilaments c)Tropomyocinunblocksthemyosinbindingsiteonmicrofilaments d)Tropomyocinblocksthemyosinbindingsiteonmicrofilaments e)Themyosinbindingsiteisopenonmicrofilaments 22)Regulationofconnexonchannelsisaccomplishedby a)Ca+2 b)Phosphorylation c)Distancebetweencells d)aandb e)bandc 23)TheOXAcomplex a)AssistsTOMinbringingmitochondrialproteinsintothematrixofthe mitochondria b)AssistTIMinbindingintegralmitochondrialproteinstotheouter mitochondriamembrane c)Involvedinbindingofintegralmembraneproteinstotheinner mitochondriamembrane d)Usedtomaintaintheprotonmotiveforceduetothevoltagedifferencein themembranepotential e)Usedtomaintainahighconcentrationofprotonsintheinnermitochondria space

24)MAP2functionsasa a)Generalmicrotubulestabilizer b)A+endstabilizer c)A+enddestabilizer d)A+andenddestabilizer e)Theonlywaytogetfreeendsfromananimalcell 25)Inthesarcomere,actinfilamentsarecappedattheplusendby________,and

attheminusendby________. a)Titinnebulin b)CapZtropomodulin c)Nebulintitin d)TropomodulincapZ e)CapZtitin

EssayQuestions

1)WhatwouldbethelongtermeffectofmutatingtheactivesitecysteineonE1? (4points) TheactivesitecysteineiswheretheCterminalglycineofUbiquitinbindsto. Withoutthisresidue,ubiquitincannotassociatewithE1,itthereforecannot transfertoE2.Thelongtermeffectwouldbenopolyubiquitnationoftarget enzymes,thuslittletonodegradationofproteins.

2)AresearcherhasconstructedamutantSar1.Thismutantalwayshasits amphipathichelixtailexposed.Whatwouldbetheoutcomeofthismutant? (4points) TheamphipathichelixtailisnormallyburiedinSar1,whichisassociated withGDP.WhenactivatedbySar1GEF,theGDPisexchangedwithGTP, whichcausesaconformationalchangeinSar1.Thisrevealstheamphipathic helixtail,whichcausesittoassociatewiththeER.Sar1recruitstheCOPII vesicles. TheoutcomeofthismutantwouldbethatitwouldALWAYSbeactiveand alwaysrecruitingCOPIIvesicles,evenwhennotneeded.

3)Aresearcherworkingontheeffectsofcholesterolontheexpressionofthe LDLreceptorinlivecellshasdecidedtoconstructsomemutantstotestsome theories.(8Points) A)ThefirstmutantconstructedcontainedaleucinerichNESaddedtothe exteriorofSREBP.Whatwouldbetheeffectofthismutantwhenlevelsof cholesterolinthegrowthenvironmentislow?

TheNESisanuclearexportsignal,thiswouldforceproteinstobeexcluded fromthenucleus.IftheSREBPcannotenterthenucleus,theLDLReceptor cannotbeexpressed.

B)Inasecondexperiment,theresearcherhadplacedaKDELsequenceontheC terminalendofS1P.Again,thecellswereplacedinalowcholesterolgrowth environment.Whatwouldbetheeffectnow?Note:thefirstandsecond experimentareINDEPENDENTofeachother,so,theNESisNOTontheSRE BPinthesecondexperiment.

Inthiscase,S1PwouldbeintheERlumen,notintheGolgi.Cleavageofthe firstsiteofSREBPwouldoccurintheER.Inlowlevelsofcholesterol,SCAP wouldexittheERandtraveltotheGolgi.BecauseSite1wascleaved,littleto noSREBPwouldbeexpectedtotravelwithSCAPtotheGolgi,however, SOMEsmallamountcouldstilltravelwithSCAPintheCOPIIvesicles. Therefore,thelevelsofLDLreceptorwoulddecreasebutwouldstillbemade atalowlevel.

4)Matchthebestdescriptiontoeachofthefollowing,thesameanswerMAYbe usedmorethanonce(1pointeach) Desmosome Hemidesmosome GapJunctions TightJunctions _______ B_ ________ _______D_________ ______ __ _ H_______ _______F_________

AdherinsJunction _______A _________

A. Linkstheactincytoskeletonsoftwocellsusingcateninsandcadherins. B. Linkstheintermediatefilamentsoftwocellsusinglinkerproteinsand cadherins. C. Linkstheactincytoskeletonofadjacentcellsthroughconnexonsand linkerproteins. D. Linkstheintermediatefilamentsofacelltotheextracellularmatrix throughlinkerproteinsandintegrins. E. Linkstheintermediatefilamentsoftwocellsusingconnexonsandtalin. F. Sealstheapicalplasmamembraneofepithelialcellsfromthebasallateral membrane.

G. Linkstheactincytoskeletontotheextracellularmatrixthroughvinculin andintegrins H. Linkstwocellsbyconnectingconnexonsthatformformpipelines joiningthecytoplasmofadjacentcells.

5)DescribewhatwouldhappeniftheRbproteinweretoloseitsabilitytobe phosphorylated.BesuretofirstexplainwhattheroleofwildtypeRbproteinis inyouranswer.(7points) RbProteinbindstoE2F,whichisanSphasegenepromoter.Bybindingup E2F,thecellisunabletomakethetransitionfromG1toSphase.ActiveG1 CdkphosphorylatesRb,whichcausesaconformationalchangeintheenzyme, releasingE2F,allowingthecelltoenterSphase ThemutantRbproteincannotbephosphorylated,thus,itcannothavethe conformatonalchangetoreleaseE2F.Thiswouldresultinacellinarrestat theG1phase,regardlessofexternalgrowthfactorsactivatingG1.Cdk 6)