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Chapter 15

Chapter 15. Chem 341 Suroviec Fall 2013. I. Introduction. Redox reaction that releases electrons into mitochondrial electron transport chain. Mitochondrial electron-transport chain Electrons transferred to other substances to participate in additional oxidation rxns

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Chapter 15

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  1. Chapter 15 Chem 341 Suroviec Fall 2013

  2. I. Introduction • Redox reaction that releases electrons into mitochondrial electron transport chain • Mitochondrial electron-transport chain • Electrons transferred to other substances to participate in additional oxidation rxns • Transferred electrons participate in sequential redox reactions of multiple redox centers in 4 enzyme complexes • During electron transfer protons are expelled making a proton gradient

  3. Contains Pyruvate dehydrogenase CAC enzymes Enzymes and redox proteins for electron transport and oxidative phosphorylation A. Mitochondrial Anatomy B. Mitochondrial Transport • Outer membrane contains proteins allows diffusion of proteins • Intermembrane space equivalent to cytosol

  4. II. Electron Transport • In a redox reaction there are electrons transferred • Reduction Potentials • Indicates a substance’s ability to accept electrons

  5. Example • Calculate the reduction potential of substance A when E = 0.5V, [Ared] = 5 x 10-6M, [Aox] = 2 x 10-4M and n = 2

  6. B. Free Energy Change • DG can be calculated from Eo’ • electrons flow spontaneously from substance with lower Eo’ to higher Eo’ Example In yeast, alcohol dehydrogenase reduces acetaldehyde to ethanol. Find DGo’

  7. Oxidation of NADH and FADH2 is carried out by electron transport chain Set of protein complexes containing redox centers with progressively greater affinities for electrons B. Sequence of Electron Transport

  8. Passes electrons from NADH to CoQ Contain FMN Contain iron – sulfur clusters 1. Complex I

  9. Contains succinate dehydrogenase Passes electrons from succinate to CoQ 2. Complex II 3. Complex III • Passes electrons from reduced CoQ to cytochrome c

  10. Q - Cycle • In complex III need to transport 1 electron at a time from CoQ through cytochromes

  11. Catalyzes one electron oxidation of 4 consecutive reduced cytochrome c molecules Reduces oxygen 4. Complex IV

  12. Chemiosmosis Free energy of electron transport is conserved by pumping H+ from matrix to intermembrane space Gradient makes ATP synthesis possible III. Oxidative Phosphorylation

  13. B. ATP synthase • Multisubunit: F1 and F0 • Binding change mechanism

  14. IV. Control of Oxidative Phosphorylation • Concentrations of intermediates and energy currency turn on/off oxidative phosphorlyation

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