生化英文习题.docx

生化英文习题.docx

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生化英文习题

八年制复习资料一

Question

1.WhilestudyingthestructureofasmallgenethatwasrecentlysequencedduringtheHumanGenomeProject,aninvestigatornoticesthatonestrandoftheDNAmoleculecontains20A’s,25G’s,30C’s,and22T’s.Howmanyofeachbaseisfoundinthecompletedouble-strandedmolecule?

A.A=40,G=50,C=60,T=44

B.A=44,G=60,C=50,T=40

C.A=45,G=45,C=52,T=52

D.A=50,G=47,C=50,T=47

E.A=42,G=55,C=55,T=42

2.ThebasesequenceofthestrandofDNAusedasthetemplatefortranscriptionhasthebasesequenceGATCTAC.WhatisthebasesequenceoftheRNAproduct?

（Allsequencesarewrittenaccordingtostandardconvention.）

A.CTAGATG

B.GTAGATC

C.GAUCUAC

D.CUAGAUG

E.GUAGAUC

3.Afour-year-oldchildwhobecomeseasilytiredandhastroublewalkingisdiagnosedwithDuchennemusculardystrophy,anX-linkedrecessivedisorder.Geneticanalysisshowsthatthepatient’sgeneforthemuscleproteindystrophincontainsamutationinitspromoterregion.Whatwouldbethemostlikelyeffectofthismutation?

A.Initialtionofdystrophintranscriptionwillbedeficient.

B.Terminationofdystrophintranscriptionwillbedeficient.

C.CappingofdystrophinmRNAwillbedefective.

D.SplicingofdystrophinmRNAwillbedefective.

E.TailingofdystrophinmRNAwillbedefective.

Answer

E.thetwoDNAstrandsarecomplementarytoeachother,withAbase-pairedwithT,andGbasepairedwithC.So,forexample,the20A’sonthefirststrandwouldbepairedwith20T’sonthesecondstrand,the25G’sonthefirststrandwouldbepairedwith25C’sonthesecondstrand,andsoforth.Whenthesearealladdedtogether,thecorrectnumbersofeachbaseareindicatedinchoiceG.Noticethat,inthecorrectanswer,A=TandG=C

E.Allsequencesarewritteninthestandardconvention（5’-3’）.TheRNAproducthasasequencethatiscomplementarytothesequenceofthetemplatestrandofDNA.Uracil（U）isfoundinRNAinplaceofthethymine（T）inDNA.Thus,theDNAtemplate5’-GATCTAC-3’wouldproducetheRNAproduct3’-CUAGAUG-5’or,writtencorrectlyinthestandarddirection,5’-GUAGAUC-3’.

A.MutationsinthepromoterpreventformationoftheRNApolymeraseIItranscriptioncomplex,andtheinitationofmRNAsynthesiswillbegreatlydecreased.AdeficiencyofdystrophinmRNAwillresultinadeficiencyintheprocductionofthedystrophinprotein,

Whichoneofthefollowingcorredtlypairsanaminoacidwithavalidchemicalcharacteristic?

A.Glutamine:

Containsahydroxylgroupintissidechain

B.Serine:

Canformdisulfidebonds

C.Cysteine:

Containsthesmallestsidechain

D.Isoleucine:

isnearlyalwaysfoundburiedinthecenterofproteins

E.Glycine:

Containsanamindegroupinitssidechain

Whichoneofthefollowingstatementsconcerningglutamineiscorrect?

A.Containsthreetitratalbegroups

B.Isclassifiedasanacidicaminoacid

C.Containsanamidegroup

D.HasEasitsone-lettersymbol

E.Migratestothecathode（negativeelectrode）duringelectrophoresisatpH7.0

Apeptidebond:

A.hasapartialdouble-bondcharacter.

B.isionizedatphysiologicpH

C.iscleavedbyagentsthatdenatureproteins,suchasorganicsolventsanhighconcentrationsofurea

D.isstaletoheatinginstrongacids

E.occursmostcommonlyinthecisconfiguration.

Whichoneofthefollowingstatementsiscorrect?

A.Theα-helixcanbecomposedofmorethanonepolypeptidechain.

B.β-sheetsexistonlyintheantiparallelform.

C.β-Bendsoftencontainproline.

D.Motifsareatypeofsecondarystructure.

E.Theα-helixisstabilizedprimarilybyionicinteractionsbetweenthesidechainsofaminoacids.

D.Inproteinsfoundinaqueoussolutions,thesidechainsofthenonpolaraminoacids,suchisoleucine,tendtoclustertogetherintheinterioroftheprotein.Glutaminecontainsanamideinitssidechain.Serineandthreoninecontainahydroxylgroupintheirsidechain.Cysteinecanformdisulfidebonds.Glycinecontainsthesmallestsidechain.

C.Glutaminecontainstwotitratablegroups,α-carboxylandα-amino.Glutamineisapolar,neutralaminoacidthatshowslittleelectrophoreticmigrationatpH7.0.Thesymbolforglutamineis“Q”.

A.thepeptidebondhasapartialdouble-bondcharacter.Unlikeitscomponents–theα-aminoandα-carboxylgroups–thecomponentsofthepeptidebonddonotacceptorgiveoffprotons.Thepeptidebondisnotcleavedbyorganicsolventsorurea,butislabiletostrongacids.Itisusuallyinthetransconfiguration

C.β-bendsoftencontainproline,whichprovidesakink.Theα-helixdiffersfromtheβ-sheetinthatitalwaysinvolvesthecoilingofasinglepolypeptidechain.Theβ-sheetoccursinbothparallelandantiparallelforms.Motifsareelementsoftertiarystructure.Theα-helixisstabilizedprimarilybyhydrogenbondsbetweenthe–C=Oand–NH-groupsofpeptidebonds.

Whichoneofthefollowingstatementsaboutproteinstructureiscorrect?

A.Proteinsconsistingofonepolypeptidecanhavequaternarystructure.

B.Theformationofadisulfidebondinaproteinrequiresthatthetwoparticipatingcysteineresiduesbeadjacenttoeachotherintheprimarysequenceoftheprotein.

C.Thestbilityofquaternarystructureinproteinsismainlyaresultofcovalentbondsamongthesubunits.

D.thedenaturationofproteinsalwaysleadstoirreversiblelossofsecondaryandtertiarystructure.

E.Theinformationrequiredforthecorrectfoldingofaproteiniscontainedinthespecificsequenceofaminoacidsalongthepolypeptidechain.

An80-year-oldmanpresentedwithimpairmentofhigherintellecutualfunctionandalterationsinmoodandbehavior.Hisfamilyreprotedprogressivedisorientationandmemorylossoverthelastsixmonths.Thereisnofamilyhistoryofdementia.ThepatientwastentativelydiagnosedwithAlzeheimerdisease.Whichoneofthefollowingbestdescribesthedisease?

A.Itisassociatedwithβ-amyloid----anabnormalproteinwithanalteredaminoacidsequence.

B.Itresultsfromaccumulationofdenaturedproteinsthathaverandomconformations.

C.Itisassociatedwiththeaccumulationofamyloidprecursorprotein.

D.Itisassociatedwiththeaccumulationofamyloidpeptideaggregates.

E.Itisanenvironmentallyproduceddiseaseuninfluencedbythegeneticsoftheindividual.

Acompetitiveinhibitorofanenzyme:

A.increasesKmwithoutaffectingVmax

B.dncreasesKmwithoutaffectingVmax

C.increasesVmaxwithoutaffectingKm

D.dncreasesVmaxwithoutaffectingKm

E.dncreasesbothKmandVmax

E.Thecorrectfoldingofaproteinisguidedbyspecificinteractionsamongthesidechainsoftheamninacidresiduesofapolypeptidechain.Thetwocysteineresiduesthatreacttoformthedisulfidebondmaybeafreatdistaqnceapartintheprimarystructure（oronseparatepolypeptides）,butarebroughtintocloseproximitybythethree-dimensionalfoldingofthepolypeptidechain.Denaturationmayeitherbereversibleorirreversible.Quaternarystructurerequiresmorethanonepolypeptidechain.Thesechainsassociatethroughnoncovalentinteractions.

D.Alzheimerdiseaseisassociatedwithlong,fibrillarproteinassembliesconsistingofβ-pleatedsheetsfoundinthebrainandelsewhere.Thediseaseisassociatedwithabnormalprocessingofanormalprotein.Theaccumulatedalteredproteinoccursinaβ-pleatedsheetconfigurationthatisneurotoxic.TheAβamyloidthatisdepositedinthebraininAlzheimerdiseaseisderivedbyproteolyticcleavagesfromthelargeramyloidprecursorprotein----asingletransmembraneproteinexpressedonthecellsurfaceinthebrainanothertissues.MostcasesofAlzheimerdiseasearesporadic,althoughatleastfivetotenpercentofcasesarefamilial.

A.Inthepresenceofacompetitiveinhibitor,anenzymeappearstohavealoweraffinityforsubstrate,butasthesubstratelevelisincreased,theobservedvelocityapproachesVm.

Whichoneofthefollowingstatementsconcerningthebingdingofoxygenbyhemoglobiniscorrect?

A.TheBohreffectresultsinaloweraffinityforoxygenathigherpHvalues.

B.Carbondioxideincreasestheoxygenaffinityofhemoglobinbybindingtotheaminoterminalgroupsofthepolypeptidechains.

C.Theoxygenaffinityofhemoglobinincreasesasthepercentsaturationincreases.

D.Thehemoglobintetramerbindsfourmoleculesof2,3-BPG.

E.Oxyhemoglobinanddeoxyhemoglobinhavethesameaffinityforprotons（H+）

TheMichaelis’constant,Km,is:

A.numericallyequlto1/2Vmax

B.dependentontheenzymeconcentration

C.independentofpH

D.numericallyequaltothesubstrateconcentrationthargiveshalf-maximalvelocity

E.increasedinthepresenceofanoncompetitiveinhibitors

Whichoneofthefollowingstatementsconcerningthecomponentsoftheelectrontransportchainiscorrect?

A.Allofthecomponentsoftheelectrontransportchainarepresentinlarge,multisubunitproteincomplexesembeddedintheinnermitochondrialmembrane.

B.OxygendirectlyoxidizescytochromeC.

C.SuccinatedehydrogenasedirectlyreducescytochromeC.

D.TheelecrontransportchaincontainssomepolypeptidechainscodedforbythenuclearDNAandcomecodedforbymtDNA

E.Cyanideinhibitselectronfolw,butnotprotonpumpingorATPsynthesis.

C.Thebindingofoxygenatonehemegroupincreasestheoxygenaffinityoftheremaininghemegroupsinthesamemolecule.CarbondioxidedecreasesoxygenaffinitybecauseitlowersthepH;alsobingdingofcarbondioxidestabilizesthetaut,deoxyform.Hemoglobinbindsonemoleculeof2,3-BPG.Deoxyhemoglobinhasagreateraffinityforprotonsand,therefor,isaweakeracid.

D.RememberKmhasthedimensionsofconcentrationandisacharacteristicofanenzymeunderagivensetof