1. Fundamentals of Biochemistry
Third Edition
Donald Voet • Judith G. Voet • Charlotte W. Pratt
Chapter 18
Electron Transport and Oxidative Phosphorylation
Copyright © 2008 by John Wiley & Sons, Inc.

2. We have made small amounts of ATP so far
The main product is the 24 H+ (24 e-) that are produced

3. Mitochondrion

4. Cristae are not necessarily uniform structures
Cristae are not necessarily uniform structures. They can vary greatly, restricting local ion movement, creating a large pH gradient.

5. How does NADH get into Matrix
Aspartate-Malate shuttle
Glycerophosphate shuttle
Insect muscle
Same power to weight ratio as a small car engine

6. Transport of Materials
ATP/ADP
Translocator
One for one
Charge problems
Phosphate
Symporter
Phosphate and H+
Both driven by pH gradient

7. Efficiency of ETC Δε°’= -0.315 V Δε°’= 0.815 V
If 1 NADH makes 2.5 ATP and it takes 30.5 kJ/mol to make 1 ATP
Efficiency of ATP synthesis is ~100kJ/mole / 218kJ/mol = 35%

9. Inhibitors of ETC
Complex I
Complex IV
Complex III

13. 10 in humans

14. Complex I

15. Rhodopsin – Model Proton Pump

16. Complex II
Complex I and Complex II are not sequential, but accept electrons from different sources.
Complex I – NADH
Complex II - succinate

17. Complex III Pass electrons from CoQ to cytochrome c
Electrons in Complex III must go from a 2 e- carrier (CoQH2) to a 1 e- carrier, cytochrome c.

18. Q cycle Q-cycle involves two cycles
Proton pumping of complex III is different from complex I or II

19. Complex IV
Requires 4 electrons
Contains Cu and Fe

20. Reaction center requires 4 electrons at once
Fe(II)-Cu(I) contributes only 3 electrons
Fourth electron comes from Y244 forming a tyrosyl radical

22. Chemiosmotic Theory 1961 Peter Mitchell Observations
OP needs intact inner mitochondrial membrane
Inner MM impermeable to H+, OH-, K+, Cl-
ET sends H+ out
Compounds that increase permeability of the MM inhibit ATP synthesis

23. Harnessing the Energy
The free energy of sending a proton against the gradient is approximately 22 kJ/mol
The free energy required to synthesize one ATP is approximately kJ/mol
It takes 2-3 H+ ions moving with the gradient to provide the energy to synthesize 1 ATP

24. ATPase portion
Membrane portion

25. F1 region of ATP synthase
Only beta subunits can catalyze ATP synthesis

27. ATP synthesis ADP + Pi bind to L site
Free energy drives conformational change
Only T site catalyzes ATP synthesis
ATP is release following next conformational change

28. pH=8 pH=5
Only the c ring moves, not alpha and beta parts
Arg210

29. PO Ratios ATP synthesized(P)/Oxygen reduce(O)
2 electrons through Complex I, III, IV result in 10 protons which rotates the c subunits one revolution thereby synthesizing 3 ATP
2 electrons from FADH2 enter complex II and result in 6 protons or ~2ATP
Estimates for glucose
2.5 ATP/NADH; 10 NADH/glucose
1.5 ATP/FADH2; 2 FADH2/glucose
2 ATP/glucose from glycolysis
2 ATP/glucose from citric acid cycle
Total = 32 ATP/glucose

30. Uncoupling Leads to Generation of Heat
Diet pill?