ch19n2-jdr - 4/27/2011 The Electron Transport System (ETS)...

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4/27/2011 1 The Electron Transport System (ETS) and Oxidative Phosphorylation (OxPhos) We have seen that glycolysis, the linking step, TCA, and b - oxidation generate a large number of reduced cofactors, mostly NADH. The pathways we discussed now pass those electrons, on reduced cofactors, to an eager receptor, oxygen. This is the ETS. The released energy is converted to the more common ATP coinage in process of OxPhos. For example, standard state free energies show: C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O D G o’ = -2823 kJ/mol And we want to see how much of that we can get back. Recall, anaerobic glycolysis only gave us 2 ATPs/glucose 16-1 Electron transport = transfer of e - from one carrier to another Oxidative phosphorylation = process by which energy released from electron transport (oxidations) is conserved in form of phosphate-bond energy of ATP What reactions produce the 4 pairs of electrons in the citric acid cycle? Isocitrate dehydrogenase a -ketoglutarate dehydrogenase Succinate dehydrogenase Malate dehydrogenase
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4/27/2011 2 A brief review, from Chapter 13, of redox chemistry Oxidation-reduction reactions = transfer of electrons from a donor (reducing agent) to an acceptor (oxidizing agent). Analogous to acid-base reaction: acid/base: proton acceptor + H + proton donor redox: electron acceptor + e - electron donor Tendency of a substance to accept electrons (to become reduced) is reflected in the standard reduction potential, E ° A o + e - A r E ° A B o + e - B r E ° B A o + B r A r + B o ∆E ° = E ° A - E ° B = reduction potential difference (acceptor) (donor)
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4/27/2011 3 oxidant + n e - reductant n = # electrons transferred The more positive the potential for a redox pair, the oxidant has greater tendency to gain electrons. Lower potential means
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This note was uploaded on 05/01/2011 for the course CH 53890 taught by Professor Raymonds during the Spring '09 term at University of Texas at Austin.

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ch19n2-jdr - 4/27/2011 The Electron Transport System (ETS)...

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