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chambers35 - Electron Transport and Oxidative...

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Electron Transport and Oxidative Electron Transport and Oxidative Phosphorylation Phosphorylation Reading: Harper’s Biochemistry pp. 130-148 Lehninger Principles of Biochemistry 3rd Ed. pp. 659-690
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OBJECTIVES OBJECTIVES To learn how NADH and FADH are re-oxidized by molecular oxygen using the electron transport chain in mitochondria, and how this generates a proton gradient across the inner mitochondrial membrane.
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Electron Transport and Oxidative Electron Transport and Oxidative Phosphorylation Phosphorylation OVERVIEW - Mitrochondria contain the series of catalysts known as the electron- transfer chain, or the respiratory chain, that collect and transport reducing equivalents and direct them to their final reaction with oxygen to form water. - The free energy made available by this “downhill” (exergonic) electron flow is coupled to the “uphill” transport of protons across a proton-impermeable membrane (inner mitrochondrial membrane). The free energy is captured as a transmembrane electrochemical potential. - The transmembrane flow of protons down their concentration gradient through specific protein channels provides the free energy for synthesis of ATP. This is performed by a membrane ATP synthase that couples proton flow to phosphorylation of ADP.
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Role of the respiratory chain of mitrochondria is the conversion of food energy to ATP. Oxidation of the major foodstuffs leads to the generation of reducing equivalents (2H) that are collected by the respiratory chain for oxidation and coupled generation of ATP.
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The term “reducing equivalent” is used to designate a single electron equivalent transferred in an oxidation- reduction reaction. Three types of electron transfers occur in oxidative phosphorylation: 1. Direct transfer of electrons, as in the reduction of Fe 3+ to Fe 2+ 2. Transfer as a hydrogen atom (H + + e - ) 3. Transfer as a hydride ion (:H - ), which bears two electrons. Most of the electrons that enter the respiratory chain arise from the action of dehydrogenases that collect electrons from catabolic pathways and funnel them into universal electron acceptors - NAD + (or NADP + ) or flavin nucleotides (FMN or FAD).
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Summary of flow of electrons and protons Summary of flow of electrons and protons through the four complexes of the
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