中大生物化学试题秋季.docx

中大生物化学试题秋季.docx

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中大生物化学试题秋季

NameClassScore

Biochemistry（I）FinalExam（fall,2004）

NOTE:

Youmustwriteyouranswerontheanswersheet!

PartI:

Forthefollowingmultiplechoicequestions,oneanswerismostappropriate（2.518=45points）.

1.Withregardtoaminoacids,whichstatementisfalse?

A）Aminoacidscanactasprotondonorsandacceptors.

B）AllaminoacidsdiscoveredinorganismareLenantiomers.

C）AnLaminoacidcanbeDextrorotary.

D）Aconjugateacid/basepairisatitsgreatestbufferingcapacitywhenthepHequalsitspK.

E）Non-standardaminoacidscanbefoundinthehydrolysisproductofaprotein.

2.AmixtureofAla,Arg,andAspinapH5.5bufferwasplacedonacationexchangecolumn（thecolumnisnegativelycharged）andelutedwiththesamebuffer.Whatistheorderofelutionfromthecolumn?

UsethesepKavalues:

terminalCOOH-2,terminalNH3+-9,R-amino-10,R-COOH-3

A）Arg,AlathenAsp

B）Arg,AspthenAla

C）Asp,AlathenArg

D）Asp,ArgthenAsp

E）Ala,AspthenArg

3.Proteinscanbechromatographicallyseparatedbytheirdifferent

A）Charge.

B）Molecularweight.

C）Hydrophobicity.

D）Affinityforothermolecules.

E）Allofabove.

4.Apeptidewasfoundtohaveamolecularmassofabout650anduponhydrolysisproducedAla,Cys,Lys,Phe,andValina1:

1:

1:

1:

1ratio.ThepeptideupontreatmentwithSanger'sreagent（FDNB）producedNP-Cysandexposuretocarboxypeptidaseproducedvaline.ChymotrypsintreatmentofthepeptideproducedadipeptidethatcontainedsulfurandhasaUVabsorbance,andatripeptide.Exposureofthepeptidetotrypsinproducedadipeptideandatripeptide.Thesequenceofthepeptideis

A）val-ala-lys-phe-cys

B）cys-lys-phe-ala-val

C）cys-ala-lys-phe-val

D）cys-phe-lys-ala-val

E）val-phe-lys-ala-cys

5.Withregardtoproteinstructure,whichstatementisfalse?

A）Thedominantforcethatdrivesawater-solubleproteintofoldishydrophobicinteraction.

B）Thenumberofhydrogenbondswithinaproteinintendstobeminimized.

C）Theconformationsofanativeproteinarepossiblythelowestenergystate.

D）Theconformationsofanativeproteinarecountless.

E）Disulfdebridgescanincreasethestabilityofaprotein.

6.Whichstructureisuniquetocollagen?

A）Thealphahelix.

B）Thedoublehelix.

C）Thetriplehelix.

D）Thebetastructure.

E）Thebetabarrel.

7.Whichproteinhasquaternarystructure?

A）Insulin.

B）Anaturalantibody.

C）Chymotrypsin.

D）Aspartatetranscarbamoylase（ATCase）.

E）Myoglobin.

8.Whichofthefollowingare"broadthemesusedindiscussingenzymereactionmechanisms"?

A）Proximitystabilization

B）Transitionstatestabilization

C）Acid-basecatalysis

D）Covalentcatalysis

E）Alloftheabove

9.Underphysiologicalconditions,whichofthefollowingprocessesisnotanimportantmethodforregulatingtheactivityofenzymes?

A）Phosphorylation

B）Temperaturechanges

C）Adenylation

D）Allostericregulation

E）Proteinprocessing

10.Theconversionofglucosetopyruvateisamultistepprocessrequiringtenenzymes.Ifamutationoccursresultinginalackofactivityforoneoftheseenzymes,whichofthefollowinghappens?

A）Theconcentrationofthemetabolicintermediatewhichisthesubstrateofthemissingenzymeislikelytoincreaseandaccumulate

B）Theconcentrationofpyruvatewillincrease

C）Thecellwillproducemoreoftheothernineenzymestomaintainsteadystate

D）Theconcentrationofthemetabolicintermediatewhichistheproductofthemissingenzymewilldecrease

E）AandD

11.Indicatewhichistrueaboutenzymes.

A）Enzymesarepermanentlychangedduringtheconversionofsubstrateintoproduct.

B）Enzymesinteractirreversiblywiththeirsubstrates.

C）Enzymeschangetheenergydifferencebetweensubstratesandproducts.

D）Enzymesreducetheenergyofactivationfortheconversionofreactantintoproduct.

E）Enzymesincreasetheenergycontentoftheproducts.

12.Considerareactionasfollows:

A+B<====>C+D,ΔG'0=+10.0Kj/mol

Howcanthisreactiongoforward?

A）Couplingofthisreactiontoahighlyexergonicreactionthroughacommonintermediate.

B）Immediateremovaloftheproducts.

C）Additionoftheappropriateenzyme.

D）AandB.

E）Alloftheabove.

13.Whichstatementisnottrueofenzymeinhibitors?

A）Acompetitiveinhibitorbindstheactivesiteoftheenzyme.

B）AllostericenzymesexhibitMichaelis-Mentonkinetics.

C）Anoncompetitiveenzymebindselsewherethantheactivesite.

D）Noncompetitiveinhibitorscannotbecompletelyovercomebyaddingmoresubstrate.

E）Competitiveinhibitioncanbecompletelyovercomebyaddingmoresubstrate.

14.YoucouldmostdramaticallydestabilizeaduplexDNAmoleculeinanaqueoussolutionby

A）Decreasingthetemperature.

B）Decreasingtheconcentrationofsalt.

C）Decreasingtheconcentrationoforganicsolvents.

D）Adjustingthep