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Unformatted text preview: Electron Transport and Oxidative Phosphorylation Stryer Chapter 18 Mitochondria Electron transfer Proton pumps/Proton gradient Movement across membranes Regulation 1 The TCA cycle, electron transport, and oxidative phosphorylation occur in the mitochondria  the energy generators of the cell Outer membrane is permeable to small molecules Inner membrane is not  ATP, pyruvate, and citrate are transported specifically ~ 2 m x 0.5 m 2 Overview of Oxidative Phosphorylation 3 NADH and FADH 2 pass their electrons to O 2 to produce H 2 O and by doing so, create a proton gradient used for OxidativePhosphorylation I II III IV 4 Redox Potentials are related to G G = RT ln K eq pH = 7 G = n F E = RT ln K eq pH = 7 G = n(23 kcal/mol/V) E X red + H + ==> X ox + 1/2 H 2 X red ==> X ox + e H + + e ==> 1/2 H 2 E = Standard reduction potential at pH 7.0 and 25 C (oxidant + e reductant) E = Change in the standard reduction potential F = Faraday constant = 23.06 kcal mol1 V1 n = number of electrons 5 A Theoretical Electrochemical Cell for Measuring Standard Redox Potentials Allows ions to cross for electrical flow 6 7 Calculating G for a reaction Pyruvate + NADH + H + <==> Lactate + NAD + Pyruvate + 2 H + + 2 e ==> Lactate E = 0.19 V NAD + + H + + 2 e ==> NADH E = 0.32 V NADH ==> NAD + = H + + 2 e E = + 0.32 V Therefore: Pyruvate + NADH + H + <==> Lactate + NAD + E = + 0.13 V G = n F E pH = 7 G = n(23 kcal/mol/V) E = 2(23 kcal/mol/V)(0.13V) = 6 kcal/mol 8 Energyrich NADH passes electrons down an energy gradient into complexes with energy differences useful for synthesizing ATP I II III IV 9 Flavin mononucleotide (FMN) FMN functions similarly to FAD; both can be in oxidized, reduced, or semiquinone (1 e ) states 10 Coenzyme Q is an important electron carrier in the mitochondrial membrane Coenzyme Q can also exist in 3 redox states: Oxidized (ubiquinone), a partially reduced semiquinone intermediate, and fully reduced (ubiquinol)....
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 Fall '06
 MichaelUhler

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