PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Figure 22-4 Electron microscopy–based three-dimensional image reconstruction of a rat liver mitochondrion.Slide 10Slide 11Figure 22-7 The malate–aspartate shuttle.Figure 22-8 The glycerophosphate shuttle.Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34X-Ray structure of ferredoxin from Peptococcus aerogenes.Slide 36Slide 37Electron microscopy–based three-dimensional structures of Complex ISlide 39Slide 40Reduction Potentials of Electron-Transport Chain Components in Resting MitochondriaSlide 42Slide 43X-Ray structure of E. coli quinol–fumarate reductase (QFR) in complex with its inhibitor oxaloacetic acid (OAA)The X-Ray structure-derived arrangement of E. coli quinol–fumarate reductase’s redox cofactors with indicated edge-to-edge distancesSlide 46Slide 47Slide 48Slide 49X-ray structures of cytochrome bc1. (a) The dimeric bovine complex is viewed perpendicular to its 2-fold axis and parallel to the membrane with the matrix belowX-ray structures of cytochrome bc1. (b) The yeast enzyme in complex with cytochrome c and the inhibitor stigmatellin viewed with a ~90° rotation about its 2-fold axisRibbon diagram of cytochrome c showing the Lys residues involved in intermolecular complex formationSlide 53Slide 54Slide 55Slide 56X-Ray structure of fully oxidized bovine heart cytochrome c oxidase. (a) View parallel to the membrane with the matrix belowX-Ray structure of fully oxidized bovine heart cytochrome c oxidase. (b) The complex as viewed from the top of Part a, along its 2-fold axisSlide 59Slide 60Slide 61Slide 62Slide 63Slide 64Slide 65Effect of inhibitors on electron transportSlide 67Coupling of electron transport (green arrow) and ATP synthesisThe redox loop mechanism for electron transport–linked H+ translocationThe Q cycleProton pump mechanism of electron transport–linked proton translocationThe proton-translocating channels in bovine COXChapter 22 Electron Transport & Oxidative PhosphorylationFrom LehningerPrinciples of BiochemistryUbiquinone (coenzyme Q)C6H12O6 + 6 O2 6 CO2 + 6 H2O6 carbon2 x 3 carbon 2 CO22 x 2 carbon 2 x 2 CO2The carbon is already converted to CO2. What is left is electrons in the form of NADH and FADH2.From Garrett & GrishamIntermembrane spaceOuter Membrane• Contains porin• Allows free diffusion of molecules with molecular weight less than 10,000Inner Membrane• Impermeable to molecules & ions{80% proteins}{30-40% lipids & 60-70% proteins}Provide inner membrane with large surface areaPorins are transmembrane channels for small moleculesFigure 22-4 Electron microscopy–based three-dimensional image reconstruction of a rat liver mitochondrion.Page 799Matrix• contains all of TCA cycle enzymes {except, succinate dehydrogenase which is located in the inner membrane}• contains circular DNA, ribosomes and enzymes required to synthesize proteins encoded within the mitochondrial genomeFrom LehningerPrinciples of BiochemistryFigure 22-7 The malate–aspartate shuttle.Page 801Figure 22-8 The glycerophosphate shuttle.Page 802Separation of functional complexes of the respiratory chainComponents of the electron transport chain can be purified from the mitochondrial inner membraneFrom LehningerPrinciples of BiochemistryElectrons transferred via NADPHElectrons transferred via NADPHFrom LehningerPrinciples of BiochemistryElectron TransportNADHFMNFe.SQCyt bFe.SCyt c1Cyt cCyt aCyt a3FADH2Fe.SO2Free Energy Relative to O2 (kcal / mol)The electron transport chainNADH (reductant) + H+ + 1/2 O2 (oxidant) NAD+ + H2OElectrons generally fall in energy through the chain - from complexes I and II to complex IV2H+ + 2e- H2orH2 2H+ + 2e- oxidized species + ne- reduced speciesor reduced species oxidized species + ne- Which way do the electrons flow?From LehningerPrinciples of BiochemistryHigh Eo' indicates a strong tendency to be reduced Nernst equation: Go' = -nFEo' Eo' = Eo'(acceptor) - Eo'(donor) Electrons are donated by the half reaction with the more negative reduction potential and are accepted by the reaction with the more positive reduction potential: Eo' positive, Go' negative If a given reaction is written so the reverse is true, then the Eo' will be a negative number and Go' will be positiveElectrochemistry reviewWhy do the electrons flow through the electron transport chain?Most oxidizingMost reducingFrom LehningerPrinciples of BiochemistryCH3CHO + 2H+ + 2e- CH3CH2OH -0.197 Vfumarate + 2H+ + 2e- succinate +0.031 VFrom LehningerPrinciples of BiochemistryFe3+ + e- Fe2+ +0.771 VThe sequence of electron transportFrom LehningerPrinciples of BiochemistryMobile electron carrierA lipid soluble coenzyme (UQ) shuttle between protein complexesElectron Carriers: FMN (Flavin Mono Nucleotide) is a prosthetic group of some flavoproteins {It is similar in structure to FAD, but lacks the adenine nucleotide} In solution FMN (like FAD) can accept 2 e- + 2 H+ to yield FMNH2 When bound at the active site of some enzymes, FMN can accept 1 e-, converting it to the half-reduced semiquinone radical. The semiquinone can accept a second e- to yield FMNH2Prosthetic groups of cytochromes Heme is a prosthetic group of cytochromes Mitochondria has 3 classes of cytochromes, designated a, b, and cThe heme iron atom can undergo a 1 electron transition between ferric and ferrous states: Fe3+ + e- Fe2+insideinsideoutsideoutsideFrom Garrett & GrishamStructure of mitochondrial cytochrome cHeme is covalently linked to the protein via S atoms- Electron transfer proteins may contain multiple iron-sulfur centers. - they transfer only one electron even when they contain two or more iron atoms, because of the close proximity of the iron atoms. Iron-sulfur centers (Fe-S)a 4-Fe center might cycle between the redox states: Fe3+3Fe2+1 (oxidized) + 1 e- Fe3+2 Fe2+2 ( reduced)X-Ray structure of ferredoxin from Peptococcus aerogenes.Ferredoxin of the cyanobacterium Anabaena 71202Fe-2S center SFeFrom LehningerPrinciples of BiochemistrySDH is on the matrix side of the IMSComplex I: NADH to Coenzyme QComplex II: Succinate to Coenzyme QComplex III:Coenzyme Q to Cytochrome cComplex IV: Cytochrome c to O2From LehningerPrinciples of BiochemistryElectron microscopy–based three-dimensional
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