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Chapter_18

Chapter_18 - Click to edit Master subtitle style Chapter 18...

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Unformatted text preview: Click to edit Master subtitle style Chapter 18 Oxidative Phosphorylation LSU Undergraduate Summer Research Scientific Research Life Sciences and Chemistry $3500 stipend & program housing College credit http://www.biology.lsu.edu/hhmiprog/u ndergrad/ Program Dates May 31 – July 30, 2010 Application Deadline Feb 10, 2010 For more information contact Sheri Wischusen 225-578- 0405 [email protected] Oxidative phosphorylation Oxidative phosphorylation I. Oxidative phosphorylation in eukaryotes takes place in mitochondria 1. Mitochondria -- 2 μ m in length and 0.5 μ m in diameters. 2. Contains enzymes of the citric acid cycle and of fatty acid oxidation 3. Outer membrane; inner membrane -- cristae; 4. The intermembrane space between the outer membrane and the inner membrane; -- oxidative phosphorylation 5. The matrix -- the citric acid cycle and fatty acid oxidation. • Outer membrane -- VDAC -- open for PO4, Cl- organic anions. • Inner membrane -- various transporters to shuffle small molecules; • Matrix (N) -- Cytosol (P) Mitochondria resemble a microbial symbiant: the All protein coding genes found in all sequenced mitochondrial genomes are contained in Reclinomonas Oxidative phosphorylation depends on electron transfer I. High energy electrons -- redox potentials and free-energy changes: The reduction potential • X- + H+ ----> X +0.5H2 • X- ----> X + e- ; H+ + e- ----> 0.5H2 • negative potential ==> electron donor • positive potential ==>electron acceptor • ∆ Go’ = -nF ∆ Eo’ • F == Faraday constant ==23.06 kcal/mol/V Potential difference measured at beginning of experiment 1 M oxidant, 1 M reductant, 1 M H+, 1 M H2 Redox potential of H+/H2 pair = 0 Oxidative phosphorylation depends on electron transfer I. High energy electrons -- redox potentials and free-energy changes Pyruvate + NADH +H + <====> lactate + NAD+ Pyruvate + 2H+ + 2e- ----> lactate Eo’ = -0.19V NAD+ + 2H+ + 2e- ----> NADH Eo’ = -0.32V Pyruvate + 2H+ + 2e- ----> lactate Eo’ = -0.19V NADH -------->NAD+ + 2H+ + 2e- Eo’ = +0.32V ∆ G0’(top)= +8.8 kcal/mol ∆ G0’(bottom)= -14.8 kcal/mol ∆ G0’(total) =8.8 -14.8 = -6.0 kcal/mol Oxidative phosphorylation depends on electron transfer II. NADH and O2 drives electron transport 1/2 O2 + NADH +H + <====> H2O + NAD+ 1/2 O2 + 2H+ + 2e- ----> H2O Eo’ = +0.82 V NAD+ + 2H+ + 2e- ----> NADH Eo’ = -0.32V ∆ G0’(total) =-52.60 kcal/mol Substantial amount of energy; Hydrolysis of ATP will release -7.3 kcal/mol For the inner mictochondrial membrane (typlically) pH out ~ pH in – 1.4, & V ~ 0.14 V Δ Proton transported out of the matrix to cytoplasm ~5.2 kcal/mol The Respiratory chain consists of four complexes...
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