Chm 635-8 - Go' = -nFEo' 1 Electron transport chain (ETC)...

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1 G o = -nF E o
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2 Electron transport chain (ETC) – Series of sequential oxidation/reduction (redox) reactions – Finally see role of oxygen – Passes electrons from NADH or FADH 2 to O 2 producing H 2 O through a series of protein complexes (source of metabolic water!) – Since NAD + and FAD are in limited supply, they must be recycled. Recycling is accomplished by oxidation and transfer of electrons to oxygen. NAD + and FAD are then available for additional oxidative metabolism. The energy released during electron transport is coupled to ATP synthesis. FOUR protein complexes in the IMM make up the ETC -Complexes I, II, III, IV -Work together in succession to catalyze redox reactions -Electrons are transferred to molecular oxygen that is then reduced to water -Electrons move through the complexes in order • Electrons from NADH enter at Complex I • Electrons from FADH 2 enter at Complex II • Flow of electrons is spontaneous and thermodynamically favorable because the next carrier has greater affinity for electrons than the previous • In each reaction, an electron donor is oxidized and an electron acceptor is reduced A reduced + B oxidized A oxidized + B reduced
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3 Complexes I – where NADH electrons enter the chain Complex II – Where FADH 2 electrons enter the chain • Electrons passed from Complex I or II to Coenzyme Q Coenzyme Q shuttles electrons to complex III Complex III shuttles electrons to cytochrome C Cytochrome C shuttles electrons to Complex IV Complex IV transfers electrons to O 2 which is then reduced to water • Flow through Complexes I, III and IV release energy which is used to pump protons across the IMM and form a “proton gradient” The Four Electron-Transport Complexes are Independent
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4 Mitchell’s postulates for chemiosmotic theory Complexes I, III, and IV “pump” protons from the mitochondrial matrix space to the intermembrane space. Complex I pumps 4 , complex III pumps 4 , and complex IV pumps 2 protons per pair of electrons transported. Electron Transport Chain • Five oligomeric assemblies of proteins associated with oxidative phosphorylation are found in the inner mitochondrial membrane Complexes I-IV contain multiple cofactors, and are involved in electron transport Complex V is ATP synthase
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5 Electrons from NADH or FADH 2 ultimately pass to oxygen. For every two electron carriers (four electrons), one O 2 molecule is reduced to two molecules of water. The electron transport chain generates no ATP directly. Its function is to break the large free energy drop from food to oxygen into a series of smaller steps that release energy in manageable amounts. The movement of electrons along the electron transport chain does contribute to chemiosmosis and ATP synthesis.
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This note was uploaded on 03/20/2012 for the course CHM 635 taught by Professor Dr.kavitashah during the Spring '11 term at Purdue University-West Lafayette.

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Chm 635-8 - Go' = -nFEo' 1 Electron transport chain (ETC)...

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