1. Homework for Electron Transport and the Proton Motive Force in Mitochondria (Due, 9/13/10)
1. In complex I (NADH-Co Q Reductase) electrons are transported from NADH to Co Q.
Write the reaction for this electron transport
NADH + CoQ  NAD+ + CoQH2
Calculate ΔEo for this reaction [use values in Karp, p. 194]
NAD+  NADH; Eo = V
CoQ  CoQH2; Eo = V
ΔEototal= Eored - Eoox = (- 0.32) = V
Based on this ΔEo, calculate ΔG.
ΔGo = -nFΔEo = -2(23.06) (0.37) = kcal/mol
(D) Can this ΔG be coupled to ATP synthesis? Explain
Yes because the free energy released greatly exceeds the amount of ΔGo
needed to synthesized ATP from ADP: ADP + Pi  ATP (+7.5 kcal/mol)

2. 2. In complex IV (cytochrome c oxidase) electrons are transported from cytochrome a3 to O2.
Write the reaction for this electron transport
½ O2 + cyt a3red  cyt a3ox + H2O
Calculate ΔEo for this reaction [use values in Karp, p. 190 or 194]
2 cyt a3ox  2 cyt a3red ; Eo = V
½ O2  H2O; Eo = V
ΔEototal = Eored - Eoox = ( ) = V
Based on this ΔEo, calculate ΔG.
ΔGo = -nFΔEo = -2(23.06) (0.43) = kcal/mol
(D) Can this ΔG be coupled to ATP synthesis? Explain.
Yes because the free energy released greatly exceeds the amount of ΔGo needed to synthesized ATP from ADP: ADP + Pi  ATP (+ 7.5 kcal/mol)

3. 3. Suppose that two components of an electron transport chain cytochromes x and y have Eo values of and +0.3, respectively.
In what direction do electrons flow between these two components?
cyt y  cyt x
(B) What is the Δ Eo for this reaction?
ΔEototal = Eored - Eoox = (+0.3) = V
(C) Based on this Δ Eo, what is the Δ G for this reaction?
ΔGo = -nFΔEo = -2(23.06) (0.10) = kcal/mol
(D) Can this ΔG be coupled to ATP synthesis? Explain.
No the ΔGo is too small. At least – 7.5 kcal/mol is required

4. 4. (A) Calculate the proton motive force (pmf) across a mitochondrial inner membrane where the electrical potential across the membrane, ψ = -100 mV and the Δ pH = 0.1.
Δp = ψ -59 Δ pH = -100 mV - 59(0.1) = = -106 mV = V
What is the Δ G for the movement of a proton down this proton generated
gradient?
ΔGo = zFΔp = (23.06) ( V) = kcal/mol
How many protons would have to be transported down this proton gradient to generate enough Δ G for the synthesis of ATP from ADP? Explain.
Based on a ΔGo of +7.5 kcal/mol for ADP  ATP, it would take a minimum of
3 protons and likely 4 or 5 for synthesis of 1 ATP