Oxidative Phosphorylation Part 1
– Electron-transport chain in mitochondria– Redox calculations– E-transport inhibitors– Building up the proton-motive force
Key topics: To Know
EOC Problem 1 is all about recognizing electron donors and acceptors…a quick review to make the rest of the chapter easy.
Mitochondia in Heart and Liver
Attempts to show more inner membrane structure in heart mitochondria compared to
liver mitochondria.
Quinones – 1 and 2 electron carriers
EOC Problem 2 looks at the ubiquinone parts and their functions. Note the isoprene length.
Difference Spectrum Vibrio harveyi. Taken from: Guerrero and Makemson 1989 Current Microbiology 18:67-73
Difference Spectrum (Reduced – Oxidized)
Entry Points to Electron Transport
EOC Problem 3: why is it that Succinate has to use FAD rather than NAD+?
Complex I Structure is Solved
Efremov, RG et al., May, 2010 Nature 465:441-445
in cytoplasmic membrane
Cytoplasm
Periplasm
Is this from mitochondria or bacteria?
Yeast Complex III and IV
Respirasome
TEM (whole, Uranyl Acetate) Superimpose Xray Structures Composite of 100’s of Images
Complex IV Complex III green red
Electron Transport Summary
EOC Problems 4 and 5 examine aspects of electron transfer and amounts of oxygen, NAD+, and other things such as inhibitors…great problems !
Summary of Electron Transport
Complex I Complex IV1NADH + 11H+
(N) + ½O2 ——> NAD+ + 10H+
(P) + H2O
Complex II Complex IVFADH2 + 6H+
(N) + ½O2 ——> FAD + 6H+
(P) + H2O
Difference in number of protons transported reflects differences in ATP synthesized.
Calculations
Differences between half cells…Example of electron transfer from NADH to ubiquinone (going from NADH through Complex I to ubiquinone):
NADH Eo’ = -.32 v
Ubiquinone Eo’ = 0.045 v
ΔEo’ = Eo’oxidized – Eo’ reduced = 0.045v – (-0.32v)
ΔEo’ = 0.365 v
ΔG’o Calculation
What is the ΔG’o for oxidation of NADH by ubiquinone
ΔG’o = - nƑΔEo’ Faraday Constant = 96,480 J/v.mole
= 96.5 kJ/v.mole
ΔG’o = - (2) 96.5 kJ/v.mole (0.365v) = - 70.4 kJ/mole
How Many “ATPs” is this worth?
Things to Know and Do Before Class
1. Where the DH’s are.
2. The electron transport players: flavin, Fe-S centers, cytochromes (and their properties), quinones, Cu++.
3. Is it the ABCs of electron transport or the BCAs?
4. Effects of electron transport inhibitors.
5. Entry points and what each complex does.
6. How to calculate ΔGo’ from ΔEo’.
7. EOC Problems: 1-5.