美国的生化考题Word格式文档下载.doc

美国的生化考题Word格式文档下载.doc

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C

O

A

B

D

A）A

B）B

C）C

D）D

6.Whichofthefollowingclassesofenzymescatalyzereactionsinvolvingthecleavageofbondsbytheadditionofwater?

A）Transferase

B）Hydrolase

C）Lyase

D）Ligase

7.Considerthefollowingreactiondata.

Alanylanine+water®

alanine

[alanylanine] [water]Rate

0.10.1 1x10-4

0.20.1 2x10-4

0.10.2 2x10-4

0.20.2 4x10-4

Thereactionis________orderoverall.

AZero

B）First

C）Second

D）Third

E）Fourth

8.Anenzymewithoutitscofactoriscalled________

A）Coenzyme

B）Apoenzyme

C）Holoenzyme

D）Isoenzyme

9.Whichofthefollowingisafunctionofproteins?

A）Structure

B）Movement

C）Transport

D）Catalysis

E）Alloftheabovearecorrect

10.Thetermproteinreferstoaminoacidpolymerswithgreaterthan________aminoacids.

A）10

B）20

C）50

D）100

11.SelectthecoenzymethatDOESNOTparticipateinelectrontransferreactions.

A）NADP

B）NAD

C）ATP

D）FAD

12.Theclassofenzymethatcatalyzesthefollowingreactionis:

A）isomerase

B）ligase

C）hydrolase

D）transferase

13.Whatisthemaximumnumberofhydrogenbondsthatonewatermoleculecanhavewithneighboringwatermolecules?

A）1

B）2

C）3

D）4

14.Whichofthefollowingaminoacidsisinvolvedindisulfidebonds?

A）cysteine

B）methionine

C）proline

D）noneofabove

15.Anapoenzymecombineswithacoenzymetoforma

A）holoenzyme

B）cofactor

C）proenzyme

D）prostheticgroup

16.Thealterationofenzymestructureonbindingofasubstratetoanactivesiteisreferredtoas

A）Enzymedenaturation

B）Enzymeinhibition

C）Inducedfit

D）Enzymeactivation

17.WhichofthefollowingpropertiesisNOTcharacteristicofenzymes?

A）Holdthesubstrateincloseproximity

B）Altertheequilibriumconstantofthereaction

C）Reducetheactivationenergy

D）Oftenuseacid-basecatalysis

18.Primaryproteinstructurerefersto

A）overallshapeofaprotein

B）repeatedpatternoffolding

C）aproteinwithmultiplesubunits

D）linearaminoacidsequence

19.Whichofthefollowingstatementsaboutaplotoftheinitialvelocity（V0）vs.theconcentrationofsubstrate（[S]）foranenzymethatfollowsMichaelis-MentenkineticsisFALSE?

A）As[S]increases,theinitialvelocityofreactionV0alsoincreases.

B）Atveryhigh[S],thevelocitycurvebecomesahorizontallinethatintersectsthey-axisatKm

C）Theshapeofthecurveisahyperbolic

D）They-axisisarate

20.Whichaminoacidisclassifiedasbasic?

A）proline

B）cysteine

C）glutamine

D）lysine

21.TheKmofanenzymaticreactionisequalto

A）theconcentrationofsubstrateatequilibrium

B）theconcentrationofproductatequilibrium

C）theconcentrationofsubstrateatone-halfmaximumvelocity（Vmax）

D）theconcentrationofenzymeatone-halfmaximumvelocity（Vmax）

22.Incompetitiveinhibition,aninhibitor:

A）bindsatseveraldifferentsitesonanenzyme.

B）bindscovalentlytotheenzyme.

C）bindsonlytotheEScomplex.

D）bindsreversiblyattheactivesite.

23.ForanenzymeobeyingMichaelis-Mentenkinetics,whatistheVmaxifV0=35µ

mole/min

when[S]=Km?

A）35µ

mole/min

B）70µ

C）105µ

D）140µ

24.Secondaryproteinstructureofrefersto

25.Thecleftinthesurfaceofanenzymewhereasubstratebindsisknownas:

A）modulatorsite

B）allostericsite

C）activesite

D）oligomericsite

26.Hydrogenbondscanoccurwhenhydrogeniscovalentlybondedtoatomslikenitrogenandoxygen.Whatpropertyofnitrogenandoxygenisimportantforthis?

A）atomicmass

B）ionizability

C）hydrophobicity

D）electronegativity

27.Succinicaciddehydrogenaseisactiveonlyincombinationwithanonproteinorganicmoleculecalledflavinadeninedinucleotide（FAD）.FADiscalleda

A）proenzyme

B）isozyme

C）apoenzyme

D）coenzyme

28.ThefollowingdatawereobtainedinastudyofanenzymeknowntofollowMichaelis-Mentenkinetics:

V0（mmol/min）Substrateadded（mM）

217

325

433

488

645

650

0.8

2

4

6

100

1,000

TheKmforthisenzymeisapproximately:

A）1mM.

B）2mM.

C）4mM.

D）6mM.

29.Towhatlevelofstructuredoa-helicesandb-sheetsbelong?

A）Primarystructure

B）Secondarystructure

C）Tertiarystructure

D）Quaternarystructure

30.AccordingtoHenderson-Hasselbalchequation,whentheconcentrationsofprotonacceptorandprotondonorarethesame,then

A）thecarboxylicacidistotallyneutralized

B）onlysaltformsarepresent

C）pH=pKa

D）pKa=log[protonacceptor]/[protondonor]

31.Thebondslinkingaminoacidstoformproteinsarecalled

A）glycosidicbonds

B）hydrogenbonds

C）aminobonds

D）peptidebonds

32.Adenaturingagentsdisruptthethree-dimensionalstructuresofmacromoleculesby

A）breakingglycosidicbonds

B）breakinghydrogenbonds

C）breakingpeptidebonds

D）breakingamidebonds

33.Allostericeffectors:

A）canbeverydifferentinstructurethanthesubstratesoftheenzyme

B）typicallybindtositesdistantfromtheactivesiteofanenzyme.

C）induceaconformationalchangeintheproteintoalteritsactivity.

D）Alloftheabove.

34.BuffersystemsareeffectivewhenthepHvaluesarewithin___pHunit（s）ofthepKavalue.

A）1

B）3

C）4

D）5

35.ThetitrationcurveoftheaminoacidglycinerevealsapK1of2.34,apI（isoelectricpoint）of5.97,andapK2of9.60.Whendissolvedinwater,whichionicspeciesismostlikelytopredominateatpH=5.97?

A）B）C）D）

36.Hydrogenbondsbetweenaminoacidsinapolypeptideoccurbetweenwhichchemicalgroups?

A）theC=OandC-Hgroups

B）theC=OandC-Rgroups

C）theC=Ogroups

D）theC=OandN-Hgroups

37.ThepHinsidecellsisnormallynearpH7.AtpH7whichstatementistrueaboutthecharges（ionizationstate）ofthealfa-carboxylandalfa-aminogroupsofanaminoaicd?

A）Thealfa-carboxylgroupis1-andthealfa-aminogroupis1+

B）Thealfa-carboxylgroupis1+andthealfa-aminogroupis1-

C）Thealfa-carboxylgroupis1-andthealfa-aminogroupisuncharged

D）Bothgroupsareuncharged（notionized）atpH7

38.Whatistheprimaryforcethatstabilizesrepeatingsecondarystructuresasfoundina-helicesandb-turns?

A）covalentbonds

B）ionicinteractions

C）hydrogenbonds

D）hydrophobicinteractions

39. 

Theeffectofanenzymeisto:

A）lowertheactivationenergy

B） 

shifttheequilibriumpositionofthereactiontowardsproducts

C） 

decreasethefreeenergyofthereaction

40.Whatistheisoelectricpoint,pI,ofglycine?

GivenpKa1=2.3,pKa2=9.6.

A）9.60

B）5.95

C）11.90

D）2.30

41.Mostenzymesare:

A）Proteins

B）Lipids

C）DNA

D）Carbohydrates

42.Thechiralityofanaminoacidresultsfromthefactthatitsacarbon:

A）hasnonetcharge

B）isacarboxylicacid

C）isbondedtofourdifferentchemicalgroups

D）issymmetric

43.Hemoglobinismadeupoffourpolypeptidechains（subunits）.Themaximumdegreeofproteinstructureshownbyhemoglobinis:

A）Quaternary

B）Tertiary

C）Secondary

D）Primary

44.BasedontheHenderson-Hasselbalchequation（shownbelow）,calculatethepHwhentheratioofaceticacidtoacetateis10to1（thepKaofaceticacidis4.76）.

A）1.00

B）3.76

C）4.76

D）5.76

45.ThepHofasampleofbloodis7.4,whilegastricjuiceispH1.4.Thebloodsamplehas:

A）0.6timesthe[H+]asthegastricjuice

B）6timeslower[H+]thanthegastricjuice

C）6,000timeslower[H+]thanthegastricjuice

D）amillion（106）timeslower[H+]thanthegastricjuice

46.Inahighlybasicsolution,pH=12,thedominantformofglycineis:

A）NH2—CH2—COOH

B）NH2—CH2—COO-

C）NH3+—CH2—COOH

D）NH3+—CH2—COO-

47.Thethree-dimensionalstructure（nativeconformation）ofproteinsisdeterminedprimarilyby

A）noncovalentinteractions.

B）theotherproteinswithwhichitformsacomplex.

C）itsaminoacidsequence.

D）molecularchaparones.

48.WhichofthefollowingforcescontributesMOSTtotheprimarystructureofaprotein?

A）