PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Cytochrome c StructureSlide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Lecture 18 - Chapters 20The Electron Transport ChainLecture 18 - Chapters 20The Electron Transport Chain“In all things in nature, there is something of the marvelous.”Aristotle(384-322 B.C.)Wall Piece #IV (1985), a kinetic sculpture by George Rhoads.1Essential QuestionEssential QuestionHow do cells oxidize NADH and FADH2 and convert their reducing potential into the chemical energy of ATP?How do cells oxidize NADH and FADH2 and convert their reducing potential into the chemical energy of ATP?2OutlineOutlineOxidation-Reduction reactionsDefinition of ξ° (standard reduction potential)′Organization of the ETC is according to increasing ξ′ values.The components of the mitochondrial ETC The path of e- flow and concomitant H+ transfer in the ETC.ROSOxidation-Reduction reactionsDefinition of ξ° (standard reduction potential)′Organization of the ETC is according to increasing ξ′ values.The components of the mitochondrial ETC The path of e- flow and concomitant H+ transfer in the ETC.ROS3Overview of the process of complete oxidation of glucose under aerobic conditions (Glycolyis + TCA Cycle + Oxidative Phosphorylation)Overview of the process of complete oxidation of glucose under aerobic conditions (Glycolyis + TCA Cycle + Oxidative Phosphorylation)Cellular Respiration: generation of High-transfer potential electron by TCA, their flow through respiratory chain, and synthesis of ATP.Cellular Respiration: generation of High-transfer potential electron by TCA, their flow through respiratory chain, and synthesis of ATP.4pyruvate Mitochondrial functions are localized in specific compartments (eukaryotes) Mitochondrial functions are localized in specific compartments (eukaryotes)Results from Endosymbiotic events, most likely from Rickettsia prowazekiiResults from Endosymbiotic events, most likely from Rickettsia prowazekii5Cellular RespirationCellular RespirationIIIIIIIVProton-motive forceProton-motive force6http://classes.midlandstech.edu/carterp/courses/bio225/chap05/lecture3.htmReduction of NAD+Reduction of NAD+7Aox + Bred Ared + BoxReduction --- Gain of e-Reduction --- Gain of e-Oxidation --- Loss of e-Oxidation --- Loss of e-B is getting oxidized B is a Reducing Agent (RA). A strong reducing agent readily donates electrons and has a negative redox potential (E0’)B is getting oxidized B is a Reducing Agent (RA). A strong reducing agent readily donates electrons and has a negative redox potential (E0’)A is getting reduced A is an Oxidizing Agent (OA). A strong oxidizing agent readily accepts electrons and has a positive redox potential (E0)′A is getting reduced A is an Oxidizing Agent (OA). A strong oxidizing agent readily accepts electrons and has a positive redox potential (E0)′The reduction potential E0 (′ ξ° )′ , or redox potential, is a measure of a molecule’s tendency to donate or accept electrons.The reduction potential E0 (′ ξ° )′ , or redox potential, is a measure of a molecule’s tendency to donate or accept electrons.8Measuring Redox Potential (electromotive force)Measuring Redox Potential (electromotive force)oxidizedoxidizedreducedreducedVoltmeterVoltmeterTogether the oxidized and the reduced forms of the substance are referred to as a ‘redox couple’Together the oxidized and the reduced forms of the substance are referred to as a ‘redox couple’1 M Fumarate1 M Succinate9ξ’o (Standard Reduction Potential) values can be used to predict the direction of redox reactionsξ’o (Standard Reduction Potential) values can be used to predict the direction of redox reactionsThe ξ o (std state reduction potential), refers to the partial reactions written as ′Oxidant + e- -> Reductant.The ξ o (std state reduction potential), refers to the partial reactions written as ′Oxidant + e- -> Reductant.pH 7.0pH 7.0Fe 3+ Fe 2+ 1 Cu 2+ Cu + 1 +0.77 +0.16 10E°= +0.77 VE°= +0.77 VAn Electrochemical CellAn Electrochemical CellE°cell = Ered + EoxE°cell = Ered + EoxE°= -0.16 VE°= -0.16 V 1. Cu+ + Fe3+ Cu2+ +Fe2+ E°cell = (-0.16) + 0.77 1. Cu+ + Fe3+ Cu2+ +Fe2+ E°cell = (-0.16) + 0.77oxoxred redE°= -0.16 VE°= -0.16 VAn Electrochemical CellAn Electrochemical CellE°cell = Ered + EoxE°cell = Ered + EoxFe2+ e- + Fe3+E°= -0.77 VE°= -0.77 V2. Cu2+ +Fe2+ Cu+ + Fe3+ E°cell = 0.16 + (-0.77)2. Cu2+ +Fe2+ Cu+ + Fe3+ E°cell = 0.16 + (-0.77)oxox red redCu2++ e- Cu+E°= +0.16 VE°= +0.16 V12Predict the direction of redox reactionsPredict the direction of redox reactionsConsider the oxidation of NADH during Oxidative Phosphorylation: NADH + H+ + ½O2 NAD+ + H2O red ox ox redThis involves the following two half reactions:(1) NAD(1) NAD++ + 2e + 2e-- + 2H + 2H++ NADH + H NADH + H+ + ξξ° = - 0.32 V (from table)′° = - 0.32 V (from table)′(2) ½ O(2) ½ O22 + 2H + 2H++ + 2e + 2e- - H H22O O ξξ° = +0.816 V (from table)′° = +0.816 V (from table)′Since we are looking for oxidation of NADH, reverse reaction 1 so that it is written as oxidation, [Note: ξ° (2) > ′ ξ° (1)]′(3) NADH + H+ NAD+ + 2H+ + 2e- ξ° = +0.32 V′Now, add reactions 2 and 3 to get the overall reaction as written above:NADH + H+ + O2 NAD+ + H2O Δξ° (whole reaction) = ′ ξ° (2) + ′ ξ° (3) ′ = (+0.816 + 0.32) V = +1.136 V13Relation between ξ° (Std Reduction Potential) and ΔG°′ (Std State Free Energy) of a redox reactionRelation between ξ° (Std Reduction Potential) and ΔG°′ (Std State Free Energy) of a redox reaction ΔG°′ = -nFΔξ°′ΔG° is the standard state free energy change of the whole reaction′Δξ° is the standard state reduction potential diference between the two half cells ′n is the number of e- transferred F is
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