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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.

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Presentation on theme: "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."— Presentation transcript:

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. (A)Write the reaction for this electron transport NADH + CoQ  NAD + + CoQH 2 (B)Calculate ΔEo for this reaction [use values in Karp, p. 194] NAD +  NADH; Eo = V CoQ  CoQH 2 ; Eo = V ΔEo total = Eo red - Eo ox = (- 0.32) = V (C)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 a 3 to O 2. (A)Write the reaction for this electron transport ½ O 2 + cyt a 3red  cyt a 3ox + H 2 O (B) Calculate ΔEo for this reaction [use values in Karp, p. 190 or 194] 2 cyt a 3ox  2 cyt a 3red ; Eo = V ½ O 2  H 2 O; Eo = V ΔEo total = Eo red - Eo ox = ( ) = V (C)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. (A) In what direction do electrons flow between these two components? cyt y  cyt x (B) What is the Δ Eo for this reaction? ΔEo total = Eo red - Eo ox = (+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 (B)What is the Δ G for the movement of a proton down this proton generated gradient? ΔGo = zFΔp = (23.06) ( V) = kcal/mol (C)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


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