BIOPOLYMERSProteinsNucleicacidsPolysaccharidesTriacylglycerolsRecoveringEnergyMONOMERSAminoacidsOxidative phosphorylationNucleotidesMonosaccharidesFattyacids> Converting electron energy into ATPNHIndirectlycoupledNADNADNADHNADHQ>Very efficient recovery of energy2-and3-CarbonINTERMEDIATES Last phase of extracting energy out of biomoleculescitricphoto-NAD*,Qacidsynthesis>FollowtheelectronscycleCONADH,QH2ADP.oxidativephosphorylationH,ONAD*,Q
Recovering Energy Oxidative phosphorylation Converting electron energy into ATP Indirectly coupled Very efficient recovery of energy Last phase of extracting energy out of biomolecules Follow the electrons
Redox ThermodynamicsOxidation is loss; reduction is gainIf you extract electrons from one donor, you must deposit them on acceptorFAD + QH2FADH, + Q个reducedReducedoxidizedoxidizedReactioncanbeexpressedashalf-reactions> Only look at one substance at a timeQH2>Q+2H++2e←→
Redox Thermodynamics Oxidation is loss; reduction is gain If you extract electrons from one donor, you must deposit them on acceptor FADH2 + Q ←→ FAD + QH2 Reduced oxidized oxidized reduced Reaction can be expressed as half-reactions Only look at one substance at a time Q + 2H+ + 2 e- ←→ QH2
RedoxThermodynamicsStandard reduction potential, EoTendency ofthe oxidized form to be reduced (accept electrons)The more + the value, the greater the tendencyActual reduction potential depends on concentrations of speciesR is gas constant (8.3145 J/K/mol)ARTeducedE=ET is temp (Kelvin)nF[Aoxidied]n=number of electronstransferredF is Faraday's constant (96,485 J/V/mol)
Redox Thermodynamics Standard reduction potential, E0’ Tendency of the oxidized form to be reduced (accept electrons) The more + the value, the greater the tendency Actual reduction potential depends on concentrations of species R is gas constant (8.3145 J/K/mol) T is temp (Kelvin) n = number of electrons transferred F is Faraday’s constant (96,485 J/V/mol)
[Areduced0.026 VE=EoInNernstequation[Aoxidized]nAt 25°C(298K):Reductionpotentialpredicts flow ofelectronsFlow from substance with lower to higher potentialLower or negative reduction potential means it is more likely todonatethanreceiveelectrons
Nernst equation At 25℃ (298K): Reduction potential predicts flow of electrons Flow from substance with lower to higher potential Lower or negative reduction potential means it is more likely to donate than receive electrons
FreeEnergy ChangesReductionpotentialpredictsflowofelectronsExample: eflow from NADH (-0.315) to Q(+0.0045)Net:TABLE15-1StandardReductionPotentialsofSomeBiological SubstancesAE=E%(e-acceptor)-E)(e-donor)Half-reaction(V)*1O,+2H+2=H00.815=0.045V-(-0.315V)SO+2H*+2=SO,+H,O0.48NO,+2H*+2c=NO,+H,O0.42=+0.360Cytochrome a, (Fe)+cytochromea, (Fe*t)0.3850.29Cytochromea(Fe)+=cytochromea(Fe)0.235Cytochrome c(Fe") +cytochromee(Fe*")0.22Cytochromen(Fe")+cytochrome(Fe2")HighestEo:O2Cytochromeh(Ft)+tcochmme.b(F2(mitochandrial)0.0770.045Ubiguinone+2H+2ubiguinol0.031Fumarate +2H+2succinateFAD+2H+2FADH, (in faoprotein)~0.0.166Oxaloacetate+2H*+2emalatePyruvate+2H+2=lactate0.185Acetaldchyde +2H*+2=ethanol0.197S+2H*+2=HS0.23Lipoic acid +2H' +2 = dihydrolipoicacid-0.29NAD'+H+2=NADH-0.315
Free Energy Changes Reduction potential predicts flow of electrons Example: e- flow from NADH (-0.315) to Q (+0.0045)