Electron Transport and Oxidative Phosphorylation

1. Electron Transport and Oxidative Phosphorylation

2. Metabolism

3. Overview of ETS/OxPhos

4. Overview of ETS/OxPhos, Fig. 18.2

5. Figure 18.2 Mitochondrion

6. Objectives A. Prove that the ATP yield from the metabolism of 1.0 mole of glucose oxidized via glycolysis and the TCA cycle pathways produces 30/32 moles of ATP.

7. Objectives (Continued) ATP Generated per Reducing Equivalent

8. Objectives (Continued) • B. Define • 1. An oxidation reaction • 2. A reduction reaction • 3. Oxidative phosphorylation • 4. An uncoupler • 5. Redox potential

9. Objectives (Continued) • C. List: 1. The components of the electron transfer chain in sequential order. 2. The sites where ATP is produced in the electron transfer chain. 3. The inhibitors of electron transfer. 4. The uncouplers of oxidative Phosphorylation. 5. The inhibitors of oxidative Phosphorylation. 6. The stimulators of electron transport

10. Objectives (Continued) • D. Compare/Contrast the glycerol-3-phosphate shuttle with the malate-Aspartate shuttle with respect to: • 1. Participating electron carriers • 2. Transport of reducing equivalents • 3. Tissue specificity

11. Objectives (Continued) • E. Discuss Mitchell's Chemiosmotic Theory of oxidative phosphorylation • 1. Diagram the system. • 2. Point out its features. • 3. Explain how the system works.

12. Objectives (Continued) • F. Discuss the function of electron transport and oxidative phosphorylation

13. Overview (Continued)

14. Overview (Continued) D Delta E’o becomes more electropositive -- Delta G’o becomes more negative ----Del

15. Oxidation: Loss of ElectronsReduction: Gain of Electrons Electron Donor<---->e- + Electron AcceptorReductant<----------------->OxidantReducing Agent<---------->Oxidizing AgentNADH + H+<--------------->NAD+Fe++<------------------------>Fe+++Lactate<---------------------->PyruvateH2O<-------------------------->½ O2FADH2<---------------------->FAD

16. I. Definitions • Oxidizing agent is the electron acceptor • Reducing agent is the electron donor.

17. I. Definitions (Continued K2) • Half-reaction or redox couple is a way to show the tendency of an element or compound to gain or lose electrons. The convention is • electron acceptor + ne <---------> electron donor

18. I. Definitions (Continued K2) • D. This tendency to gain or lose electrons is quantified by the standard redox potential (E0'). • 1. the more positive the standard redox potential, the stronger the attraction for electrons. • 2. the most positive couple always accepts electrons from the least positive couple.

20. I. Definitions (Continued K3) • E. When the concentrations of electron donor and electron acceptor of a particular redox couple are equal, then • ΔE0N = E0N(electron acceptor) - E0N(electron donor)

21. I. Definitions (Continued K2) F. If the concentrations of the electron donor and electron acceptor are not equal then the Nernst Equation is used to calculate the reduction potential for the half-reaction. Once the "corrected" E' is calculated the overall E' for the reaction is calculated using the equation on previous slide.

22. I. Definitions (Continued K2) • where E& 0 = standard redox potential for half reaction in volts • R = gas constant = 8.31 Joule/deg K/mole • T = Absolute Temperature in 0K degrees • n = number of electrons transferred

23. Half Reactions/Redox Couple, p. 508

24. Half Reactions/Redox Couple Delta Go’ = -n F Delta E Delta Go’ = -2 (23,062)(+0.13) = -6.0 kcal/molDDetD ΔG0' = -n F E0' Therefore when the free energy change is negative, the redox potential is positiveTherefore

25. Electron Transport Chain Delta E’o becomes more electropositive ------ Delta Go’ becomes more negative --------D

26. Components of the ETS

27. ElectronCarriers

28. Respiratory Chain Components

29. II. Respiratory Chain Components (K3) 1. Coenzymes a. NAD(H) (1) carries one proton and two electrons (hydride) (b) carbon 4 of the pyrimidine ring is the "active" site (c) unbound

30. NADH

31. NAD+

32. + NADH NAD+

33. II. Respiratory Chain Components Continued • FAD(H2) • (1) Carries two protons and two electrons • (2) Isoalloxazine ring is active moiety • (3) Is a prosthetic group

34. II. Respiratory Chain Components Continued FAD(H2) Figure 14.15 in text And on Blackboard

35. FADH2 FAD

36. Reactive Isoalloxazine Ring

37. II. Respiratory Chain Components Continued C. FMN(H2) (1) Carries two protons and two electrons (2) Isoalloxazine ring is active moiety (3) Is a prosthetic group

38. II. Respiratory Chain Components Continued

39. Iron-Sulfur Clusters (Fe++S • NADH-CoQ oxidoreductase prosthetic Group • Receives electrons from FMNH2 and transfers them to CoQ • No protons are released • Non-heme iron proteins

40. Iron-Sulfur Clusters (Fe++S). Fig. 18.9

41. II. Respiratory Chain Components Continued D. CoQ (not a coenzyme in the strict sense) or Ubiquinone (1) gains the equivalent of two electrons and two protons (2) lipid in quinone class of compounds; variable chain lenth (3) quinone structure is active site

42. Coenzyme Q or Ubiquinone (Oxidized)

43. Coenzyme Q or ubiquinone (Reduced)

44. CoQ (ox) CoQH2

45. II. Respiratory Chain Components Continued

46. II. Respiratory Chain Components Continued: Electron Transfer Reactions catalyzed by NADH-CoQ oxidoreductase Complex I

47. II. Respiratory Chain Components Continued: Electron Transfer Reactions catalyzed by Succinate Dehydrogense

48. Overall Reactions NADH + Q + 5 H+matrix NAD+ + QH2 + 4 H+cytoplasm FADH2 + Q  FAD + QH2 (No protons pumped) QH2 + 2 Cyt cox + 2 H+matrix Q + 2 Cyt cred+ 4 H+cytoplasm 2 Cyt cred + 4 H+matrix + O2  2 Cyt cox+ 1 H2O + 2 H+cytoplasm

49. II. Respiratory Chain Components (Cont)

50. II. Respiratory Chain Components (Cont)