7 - Membrane Biogenesis IV Mitochondria & Chloroplasts

7 - Membrane Biogenesis IV Mitochondria &...

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Overview Bioenergetics: mitochondria and chloroplasts Mitochondrial genetics and disease Mitochondrial protein import Mitochondria and apoptosis Mitochondria and aging Mitochondrial dynamics
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Mitochondria (and chloroplasts) are thought to have evolved from endosymbiotic bacteria
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Structure of mitochondria and chloroplasts
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Molecular Biology of the Cell , Fifth Edition (© Garland Science 2008) Mitochondrial ultrastructure
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Efficient ATP production requires mitochondria DiMauro and Schon (2004) N Engl J Med Anaerobic glycolysis yields 2 ATP molecules : glucose + 2 NAD + + 2 ADP +2 P i 2 pyruvate + 2 NADH + 2 H + + 2 ATP + 2 H 2 O Complete oxidation of glucose to CO 2 and H 2 O yields ~ 30 ATP molecules : requires the TCA cycle, the electron transport chain, and oxidative phosphorylation, all localized to mitochondria. β -oxidation of fatty acids also occurs in mitochondria. The spirals represent reactions of the β -oxidation pathway, resulting in the liberation of CoA and the reduction of flavoprotein. ANT adenine nucleotide translocator, CACT carnitine–acyl- carnitine translocase, CoQ coenzyme Q, CPT carnitine palmitoyltransferase, DIC dicarboxylate carrier, ETF electron- transfer flavoprotein, ETF- DH electron-transfer dehydrogenase, FAD flavin adenine dinucleotide, PDHC pyruvate dehydrogenase complex
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Figure 2-82 Molecular Biology of the Cell (© Garland Science 2008) The TCA cycle generates the activated carrier molecules NADH and FADH 2 from acetyl CoA • Tricarboxylic acid (TCA) cycle = citrate cycle= Krebs cycle • acetyl CoA generated from pyruvate or fatty acid β -oxidation • reduced flavin adenine dinucleotide (FADH 2 ) and reduced nicotinamide adenine dincucleotide (NADH) are high energy electron carriers. • NADH and FADH 2 are substrates for the electron transport chain.
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In the electron transport chain, electron transfer reactions are coupled to proton pumping Respiratory complexes in the inner membrane generate proton gradient and membrane potential : • Complex I = NADH-CoQ reductase • Complex III = CoQH 2 -cytochrome c reductase; cytochrome bc 1 complex • Complex IV = Cytochrome c oxidase • Complex II = Succinate-CoQ reductase; succinate dehydrogenase • Complexes I, III, IV pump protons into the intermembrane space, using the energy from electron flow. • Ubiquinone (=Coenzyme Q) and cytochrome c are mobile electron carriers between the respiratory complexes. Proton-motive force (-220 mV)= electric potential (-160 mV) + the proton gradient ( pH, 60 mV) Alberts et al
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The proton motive force is used to drive ATP synthesis by Complex V Complex V is the ATP synthase : ATP synthesis by ATP synthase is coupled to the movement of protons down their concentration gradient. "Respiratory control": If ATP synthesis is stopped, proton pumping by the ETC also stops. The proton motive force builds up and prevents further functioning of the ETC.
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7 - Membrane Biogenesis IV Mitochondria &...

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