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Transcript
LECTURE9–20thMarch2015 Energy -Metabolism=Chemicalandenergytransformationsincells. -ComplexSystemrequiresenergy.Humansareexampleofcomplexsystem, whichmeanshumansneedenergytokeepgoing;energybuildsus. -Energyisconserved.Itisstored.Soifthereischemicalreactionthatliberated energy,theenergyisgoingtogosomewhere,caneitherbeusedbythecellto dosomework,ordissipatedasheat;itisnotdestroyed. βOxidation - Initialprocessingoflipids - Lipidshydrolysedintofreefattyacidsandglycerol - Thefattyacidsarebeingconvertedintomoleculecalled AcetylCoA - AcetylCoA=gatewaytothecitricacidcycle - ProducesFADH2andNADH HarvestingChemicalEnergy -ATPisusedtodrivethecellularprocesses ATP -Adenineunitwithribosesugarand3phosphategroups -Thebondsthatholdthephosphategroupsarehigh-energybonds,sowhen oneofthephosphategroupsisbrokenoff,theenergyreleasedcanbeusedby celltodosomething. -Example:SubstrateAbrokendowntoitsproduct,energyisbeingreleased whichthenusedtostickphosphategroupontoADPtogiveATP,andthen whenthat’sremovedtheenergycanusedtodrawsomeotherreaction -Energyreleasedfromanexergonicreaction(energyisreleased)isusedto phosphorylateADP,whichisthendephosphorylatedtodriveanendergonic reaction(energyisabsorbed) EnzymeCatalyticCycle 1.Thesubstrate,sucrose,consistofglucoseandfructosebondedtogether 2.Thesubstratebindstotheenzyme,forminganenzyme-substratecomplex 3.Thebindingofthesubstrateandenzymeplacesstressontheglucosefructosebond,andthebondbreaks 4.Productsarereleaseandtheenzymeisfreetobindothersubstrates. CellularRespiration -Breakdownmolecules(mostlyglucose)toproduceenergy -Glycolysis->TheCitricAcidCycle->ElectronTransport -Inaerobiccellularrespiration,Oxygenisthefinalelectronacceptorofthe electrontransportsystem;theenergyreleasedfromreducedelectroncarriers isusedtocreateaprotongradientacrossthemitochondrialinnermembrane 1.Glycolysis - Occursinthecytosol - Initialprocessingofglucose(fuelmoleculesofcells) - Glycolysisisanetproducerofenergy - Glycolysisisthefirstchoiceratherthanbetaoxidation - Acetyl-CoAisproducedbyprocesscalleddecarboxylationofpyruvate - Forglycolysistocontinue,thecellrequireNAD+ - Startingmaterial=6-carbon-glucose - Product=2pyruvicacid,2ATP,2NADHand2water 2.TheCitricAcidCycle(KrebsCycle) - Occursinmatrixmitochondria - TheoxidationofpyruvatetoAcetyl-CoA - Theoxidativestepsarecoupledtothereductionofelectron carriers - Reducedelectroncarriersareproduced - Startingmaterial=AcetylCoAand4-carbonmolecule - Product=2ATP,4CO2,6NADH,2FADH2 - TheconversionofpyruvatetoAcetylCoAresultsinCO2 isproducedandthefirstNADHisformed - Inthefinalstep,the4-carbonmoleculeisfurtheroxidizedand hydrogenthatareremovedareusedtoformNADHandFADH2 3.ElectronTransportChain - Have10NADH,and2FADH2fromglycolysisandKrebscycle - Occursinthemitochondrialmembrane - NADHisbeingconvertedbacktoNAD+,anditgoesback totheKrebsCycle,picksupanothercoupleofelectrons, runsbackagaintotheElectronTransportChain. - NADHdehydrogenase=pullsthehydrogenionfrom NADH(temporaryelectroncarrier) - Theelectronbeingpasseduptooneenzymescomplextoanother withaseriesofredoxreaction.Everytimethathappens,itispassed downwithaslightlydifferentenergystates.Theenergylossisused topumpthehydrogenionfrommitochondrialmatrixacrossthe inter-membranespace. - ElectronsdonatedbyNADHandFADH2fromthecitricacidcycle driveprotonpumpscoupledtoATPsynthesis - Produce:6H2Oand26-28ATP Fermentation - ATPproductionwithoutoxygen - Thepyruvateproducedbyglycolysisisconvertedtolactateorethanol - InvolvesglycolysisthatconsumeNADHproducedinglycolysisfor reductionofpyruvate - RecyclesNAD+forreuseinATPproduction Mitochondria - Thesiteofcellularrespiration - Releaseenergybyoxidationofsugars - ReleaseenergystoredinATP - Cellswithhighlevelofmetabolicactivityhavelargenumbersof mitochondria - Theproteincomplexesoftheelectrontransportsystemofchloroplast createaprotongradientthatdrivesATPsynthesis Chemiosmosis - Movementsofionsacrossaselectivelypermeablemembrane,down theirelectrochemicalgradient.Morespecifically,itrelatestothe generationofATPbythemovementofhydrogenionsacrossa membraneduringcellularrespirationorphotosynthesis. - ATPisbeingsynthesizeherewithATPSynthase - TheenergyforthesynthesisofATPduringtheflowofelectronsdown therespiratorychainisprovideddirectlybythediffusionofprotons - Protonsarepumpedoutofmitochondrialmatrixintotheintermembranespaceofthemitochondria 1Glucose=36ATPwith2ATPproducedfromglycolysisisbeingusedagainto producedNADH2inglycolysis)