SM_c19OxidativePhosphorylationandPhotophosphorylation

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1、c19OxidativePhosphorylationandPhotophosphorylation.qxd11/30/127:15PMPageS-223chapterOxidativePhosphorylationandPhotophosphorylation191.Oxidation-ReductionReactionsTheNADHdehydrogenasecomplexofthemitochondrialrespira-32torychainpromotesthefollowingseries

2、ofoxidation-reductionreactions,inwhichFeandFerepresenttheironiniron-sulfurcenters,Qisubiquinone,QH2isubiquinol,andEistheenzyme:(1)NADHHE-FMN88nNADE-FMNH2388nE-FMN2Fe2(2)E-FMNH22Fe2H23(3)2Fe2HQ88n2FeQH2Sum:NADHHQ88nNADQH2Foreachofthet

3、hreereactionscatalyzedbytheNADHdehydrogenasecomplex,identify(a)theelectrondonor,(b)theelectronacceptor,(c)theconjugateredoxpair,(d)thereducingagent,and(e)theoxidizingagent.AnswerOxidation-reductionreactionsrequireanelectrondonorandanelectronacceptor.Recal

4、lthatelectrondonorsarereducingagents;electronacceptorsareoxidizingagents.(1)NADHistheelectrondonor(a)andthereducingagent(d);E-FMNistheelectronac-ceptor(b)andtheoxidizingagent(e);NAD/NADHandE-FMN/E-FMNH2areconjugatere-doxpairs(c).3(2)E-FMNH2istheelectron

5、donor(a)andreducingagent(d);Feistheelectronacceptor32(b)andoxidizingagent(e);E-FMN/E-FMNH2andFe/Feareredoxpairs(c).2(3)Feistheelectrondonor(a)andreducingagent(d);Qistheelectronacceptor32(b)andoxidizingagent(e);andFe/FeandQ/QH2areredoxpairs(c).2.AllPa

6、rtsofUbiquinoneHaveaFunctionInelectrontransfer,onlythequinoneportionofubiquinoneundergoesoxidation-reduction;theisoprenoidsidechainremainsunchanged.Whatisthefunctionofthischain?AnswerThelongisoprenoidsidechainmakesubiquinoneverysolubleinlipidsandallowsitt

7、odiffuseinthesemifluidmembrane.Thisisimportantbecauseubiquinonetransferselec-tronsfromComplexesIandIItoComplexIII,allofwhichareembeddedintheinnermito-chondrialmembrane.S-223c19OxidativePhosphorylationandPhotophosphorylation.qxd11/30/127:15PMPageS-224S-224

8、Chapter19OxidativePhosphorylationandPhotophosphorylation3.UseofFADRatherThanNADinSuccinateOxidationAllthedehydrogenasesofglycolysisandthecitricacidcycleuseNAD(EforNAD/NADHis0.32V)aselectronacceptorexceptsuccin