Oxidative Phosphorylation Chapter 19, pp. 659-690

1. Oxidative Phosphorylation Chapter 19, pp. 659-690

2. 6 carbon C6H12O6 + 6 O2  6 CO2 + 6 H2O 2 x 3 carbon 2 CO2 2 x 2 carbon The carbon is already converted to CO2. What is left is electrons in the form of NADH and FADH2. 2 x 2 CO2

5. NAD+/NADH Coenzyme Q

6. FAD/FADH2 Hemes

7. Iron-Sulfur Centers

8. Which way do the electrons flow? 2H+ + 2e- H2 or H2  2H+ + 2e- oxidized species + ne- reduced species or reduced species  oxidized species + ne-

9. Electrochemistry review High Eo' indicates a strong tendency to be reduced • Nernst equation: Go' = -nFEo' • Eo' = Eo'(acceptor) - Eo'(donor) • Electrons are donated by the half reaction with the more negative reduction potential and are accepted by the reaction with the more positive reduction potential: Eo’ positive, Go' negative • If a given reaction is written so the reverse is true, then the Eo' will be a negative number and Go' will be positive

10. Why do the electrons flow through the electron transport chain? Most oxidizing Most reducing

11. CH3CHO + 2H+ + 2e- CH3CH2OH -0.197 V fumarate + 2H+ + 2e- succinate +0.031 V Fe3+ + e- Fe2+ +0.771 V

14. Determining the sequence of electron carriers using inhibitors of electron transfer Those that are reduced are blue. Those that stay oxidized are pink

15. Complex I: NADH to Coenzyme Q Complex II: Succinate to Coenzyme Q Complex III:Coenzyme Q to Cytochrome c Complex IV: Cytochrome c to O2 SDH is on the matrix side of the IMS

17. SDH

18. Coenzyme Q

19. Complex III structure (half of the functional dimer)

21. Cytochrome c

24. Core of Complex IV is comprised of 3 subunits Subunit II CuA (2 Cu) Subunit III CuB Subunit I heme a, heme a3, and CuB

28. O2 + 4 H+ + 4 cyt c (Fe2+) 2 H2O + 4 cyt c (Fe3+)

29. Proton-motive force

31. Coupling of electron transfer and ATP synthesis in isolated mitochondria Dinitrophenol causes dissipation of the protn gradient and thus uncouples. Inhibits ATP Synthase

33. Hydrolysis of ATP catalyzed by ATP synthase (reverse reaction) Mechanism of ATP Synthase Expected: H218O ATP ADP + [P(16O)3 (18O)]3- Singly labeled Found: H218O ATP ADP + [P18O4]3- Totally exchanged Conclusion: ATP is stabilized relative to ADP on the surface of F1

34. The proton gradient drives the release of ATP from the enzyme surface ATP is stabilized by binding to enzyme. Free energy required for its release is provided by proton-motive force.

35. Model of ATP Synthase complex 33

36. ADP ATP

37. ADP ATP

40. Binding-change model for ATP synthase

42. Loose binding (moderate) affinity for ligands Catalytically inactive L T O High affinity for ligands Catalytically active Very low affinity for ligands Catalytically inactive

43. Binding-Change Mechanism Flow of 3 H+ into the matrix g subunit rotates as H+ passes through the Fo subunit from the intermembrane space. Structural change in each active site occurs as a result of g subunit rotation

46. Shuttle systems are required for mitochondrial oxidation of cytosolic NADH

49. Uncoupled mitochondria in brown fat produce heat

50. Regulation of the ATP-producing pathways