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1、8CELLULARENERGETICSComputer-generatedmodelofasectionofamitochon-drionfromchickenbrain,basedonathree-dimensionalelectrontomogram.[T.FreyandC.Mannella,2000,TrendsBiochem.Sci.25:319.]hemostimportantmoleculeforcapturingandtrans-glucose,calledglycolysis,occurinthecytosolinbotheu-ferringfr
2、eeenergyinbiologicalsystemsisadenosinekaryotesandprokaryotesanddonotrequireoxygen(O2).Ttriphosphate,orATP(seeFigure2-24).CellsusetheThefinalsteps,whichrequireoxygen,generatemostoftheenergyreleasedduringhydrolysisoftheterminal“high-ATP.Ineukaryotes,theselaterstagesofaerobicoxidationen
3、ergy”phosphoanhydridebondinATPtopowermanyoccurinmitochondria;inprokaryotes,whichcontainonlyenergeticallyunfavorableprocesses.Examplesincludetheaplasmamembraneandlackinternalorganelles,manyofsynthesisofproteinsfromaminoacidsandofnucleicacidsthefinalstepsoccurontheplasmamembrane.Thefin
4、alfromnucleotides(Chapter4),transportofmoleculesagainststagesoffattyacidmetabolismsometimesoccurinmito-aconcentrationgradientbyATP-poweredpumps(ChapterchondriaandgenerateATP;inmosteukaryoticcells,how-7),contractionofmuscle(Chapter19),andmovement(beat-ever,fattyacidsaremetabolizedtoCO
5、2andH2Oining)ofcilia(Chapter20).Althoughotherhigh-energymole-peroxisomeswithoutproductionofATP.culesoccurincells,ATPistheuniversal“currency”ofInphotosynthesis,lightenergyisconvertedtothechem-chemicalenergy;itisfoundinalltypesoforganismsandicalenergyofphosphoanhydridebondsinATPandstor
6、edmusthaveoccurredintheearliestlife-forms.inthechemicalbondsofcarbohydrates(primarilysucroseThischapterfocusesonhowcellsgeneratethehigh-andstarch).Oxygenalsoisformedduringphotosynthesis.InenergyphosphoanhydridebondofATPfromADPandin-2organicphosphate(HPO4).Thisendergonicreaction,whic
7、histhereverseofATPhydrolysisandrequiresaninputof7.3kcal/moltoproceed,canbewrittenasOUTLINE234PiHADP¡ATPH2O8.1OxidationofGlucoseandFattyAcidstoCO222wherePirepresentsinorganicphosphate(HPO4).The8.2ElectronTransportandGenerationofenergytodrivethisreactionisproducedprimarilybytw
8、otheProton-M
