生物化学英文版习题

I.FuelMetabolismPART1:StructureandFunctionofProteinDirections:Eachofthenumbereditemsorincompletestatementsinthissectionisfollowedbyanswersorbycompletionsofthestatement.Selecttheoneletteredanswerorcompletionthatisbestineachcase.Questions9and10Usethestructuretoanswerquestions9and10：Asp-Ala-Ser-Glu-Val-Arg9.TheC-terminalaminoacidofthehexapeptideshownis(A)alanine(B)asparagine(C)aspartate(D)arginine10.AtphysiologicpH(7.4),thishexapeptidewillcontainanetchargeof(A)-2(B)-1(C)0(D)+1(E)+211.Whichoneofthefollowingtypesofbondsiscovalent?(A)Hydrophobic(B)Hydrogen(C)Disulfide(D)Electrostatic13.Whichoneofthefollowingconditionscauseshemoglobintoreleaseoxygenmorereadily?(A)Metabolicalkalosis(B)Increasedproductionof2,3-bisphosphoglycerate(BPG)(C)Hyperventilation,leadingtodecreasedlevelsofCO2intheblood(D)Replacementoftheβsubunitswithγsubunits14.Productionofwhichofthefollowingproreinswouldbemostdirectlyaffectedinscurvy?(A)Myoglobin(B)Collagen(C)Insulin(D)Hemoglobin15.Theactivesiteofanenzyme(A)isformedonlyafteradditionofaspecificsubstrate(B)isdirectlyinvolvedinbindingofallostericinhibitors(C)residesinafewadjacentaminoacidresiduesintheprimarysequenceofthepolypeptidechain(D)bindscompetitiveinhibitors16.AnenzymecatalyzingthereactionE+S=ES→E+Pwasmixedwith4mMsubstrate.Theinitialrateofproductformationwas25%ofVm.TheKmfortheenzymeis(A)2mM(B)4mM(C)9mM(D)12mM(E)25mM17.Thevelocity(v)ofanenzyme-catalyzedreaction(A)decreasesasthesubstrateconcentrationincreases(B)islowestwhentheenzymeissaturatedwithsubstrate(C)isrelatedtothesubstrateconcentrationatlhVm(D)isindependentofthepHofthesolutionQuestions18and19Refertothefollowingreactionwhenansweringquestions18and19.Fumarate+H20↔malatefumarase18.Fumarasecatalyzestheconversionoffumaratetomalate.IthasaKmof5μMforfumarateandaVmaxof50μmol/min/mgofproteinwhenmeasuredinthedirectionofmalateformation.Theconcentrationoffumaraterequiredtogiveavelocityof25μmol/min/mgproteinis(A)2μM(B)5μM(C)10μM(D)20μM(E)50μM19.TheKmforfumaraseisapproximately5μMforfumarate.Thefumarateconcentrationinmitochondriaisapproximately2mM.Ifthefumarateconcentrationdroppedto1mM,thereactionratewould(A)increaseslightly(B)decreaseslightly(C)decreasebyonehalf(D)stayexactlythesame20.Hexokinaseandglucokinasebothcatalyzethephosphorylationofglucosetoglucose6-phosphate.ThevaluesofKmfortheenzymesare10μMand0.02M,respectively.Ifbloodglucoseis5mMunderfastingconditionsand20mMafterahigh-carbohydratemeal(A)hexokinasewillfunctionnearitsVmaxunderfastingconditions(B)glucokinasewillfunctionnearitsVmaxunderfastingconditions(C)hexokinasewillfunctionatlessthanone-halfVmaxafterahigh-carbohydratemeal(D)glucokinasewillfunctionatlessthanone-halfVmaxafterahigh-carbohydratemeal21.Acompetitiveinhibitorofanenzyme(A)increasesKmbutdoesnotaffectVmax(B)decreasesKmbutdoesnotaffectVmax(C)increasesVmaxbutdoesnotaffectKm(D)decreasesVmaxbutdoesnotaffectKm(E)decreasesbothVmaxandKmQuestions22-25Refertothegraphwhenansweringquestions22-25.22.ThevalueofKmfortheenzymedepictedbycurveAis(A)0.5mM(B)1mM(C)2mM(D)1μmol/min/mg(E)10μmol/min/mg23.ThevalueofVmfortheenzymedepictedbycurveAis(A)0.1μmol/min/mg(B)1μmol/min/mg(C)10μmol/min/mg(D)0.5mM(E)2mM24.CurveBdepictstheeffectofaninhibitoronthesystemdescribedbycurveA.Thisinhibitor(A)isacompetitiveinhibitor(B)isanoncompetitiveinhibitor(C)increasestheVmax(D)decreasestheKm25.CurveCdepictstheeffectofadifferentinhibitorofthesystemdescribedbycurveA.Thissecondinhibitor(A)isacompetitiveinhibitor(B)isanoncompetitiveinhibitor(C)increasestheVmax(D)decreasestheKmanswer：DBCBBDDCBBAAACABDirections:Eachgroupofitemsinthissectionconsistsofletteredoptionsfollowedbyasetofnumbereditems.Foreachitem,selecttheoneletteredoptionthatismostcloselyassociatedwithit.Eachletteredoptionmaybeselectedonce,morethanonce,ornotatall.Questions33-37Matcheachcharacteristicbelowwiththeproteinitbestdescribes.(A)Hemoglobin(B)Myoglobin(C)Collagen(D)Insulin33.RequiresvitaminCforitssynthesis34.Hasoneoxygenbindingsiteandonepolypeptidechain35.Containsfourmoleculesofheinepermoleculeofprotein36.Isconvertedintoatriplehelixduringitssynthesis37.Iscomposedoftwopolypeptidechainsjoinedbydisulfidebondsanswer：CBACD9-D.Byconvention,peptidesaredrawnwiththeN-terminalaminoacidontheleftandtheC-terminalaminoacidontheright.Therefore,thispeptidecontainsarginineatitsC-terminus.10-B.TheN-terminalaspartatecontainsapositivechargeonitsN-terminalaminogroupandanegativechargeonthecarboxylgroupofitssidechain.Glutamatecontainsanegativechargeonthecarboxylgroupofitssidechain.TheC-terminalargininecontainsanegativechargeonitsC-terminalcarboxylgroupandapositivechargeonitssidechain.Thus,theoverallchargesare+2and-3,whichgivesanetchargeof-1.11-C.Disulfidebondsarecovalent.13-B.Increased[H+],BPG,andCO2decreasetheaffinityofHbAforO2.Fetalhemoglobin(HbF=(α2Y2)hasagreateraffinityforO2thanHbA(α2β2).IncreasedBPGwouldcauseO2tobemorereadilyreleased.14-B.ScurvyiscausedbyadeficiencyofvitaminC.ThehydroxylationofprolineandlysineresiduesincollagenrequiresvitaminCandoxygen.Globinsynthesismightbeindirectlyaffectedbecauseabsorptionofironf