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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 µm x 0.5 µm 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 ∆ Gº’ ∆ Gº’ = RT ln K eq ’ pH = 7 ∆ Gº’ = n F ∆ E ’ = RT ln K eq ’ pH = 7 ∆ Gº’ = 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 ∆ Gº’ 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 ∆ Gº’ = – n F ∆ E ’ pH = 7 ∆ Gº’ = – 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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This note was uploaded on 01/16/2012 for the course BIOLCHEM 415 taught by Professor Michaeluhler during the Fall '06 term at University of Michigan.
 Fall '06
 MichaelUhler

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