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Question 1: The standard reduction potential for the the cytochrome c Fe3+/Fe2+ redox couple and for the dioxygen/water redox couple. Part a: Use these values, and the relevant equation, to compute the standard free energy change for the transfer of 4 electrons from cytochrome c to dioxygen. Part b: Next, compute the free energy needed to pump four protons across the mitochondrial membrane, using the relevant equation and values of -.14V for Δψ and 1.4 for ΔpH. Part c: If energy conservation by cytochrome c oxidase involved only the four pumped protons (and standard conditions applied), what would be the efficiency of energy conservation at this step? (what is the ratio [energy conserved in the gradient] / [redox energy used] ?)

Question 1: The standard reduction potential for the the cytochrome c Fe3+/Fe2+ redox couple and for the dioxygen/water redox couple. Part a: Use these values, and the relevant equation, to compute the standard free energy change for the transfer of 4 electrons from cytochrome c to dioxygen. Part b: Next, compute the free energy needed to pump four protons across the mitochondrial membrane, using the relevant equation and values of -.14V for Δψ and 1.4 for ΔpH. Part c: If energy conservation by cytochrome c oxidase involved only the four pumped protons (and standard conditions applied), what would be the efficiency of energy conservation at this step? (what is the ratio [energy conserved in the gradient] / [redox energy used] ?)

Biochemistry
Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
Section: Chapter Questions
Problem 1P
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Question 1: The standard reduction potential for the the cytochrome c Fe3+/Fe2+ redox couple and for the dioxygen/water redox couple.

Part a: Use these values, and the relevant equation, to compute the standard free energy change for the transfer of 4 electrons from cytochrome c to dioxygen.

Part b: Next, compute the free energy needed to pump four protons across the mitochondrial membrane, using the relevant equation and values of -.14V for Δψ and 1.4 for ΔpH.

Part c: If energy conservation by cytochrome c oxidase involved only the four pumped protons (and standard conditions applied), what would be the efficiency of energy conservation at this step? (what is the ratio [energy conserved in the gradient] / [redox energy used] ?)

TABLE 18.1 Standard reduction potentials of some reactions Oxidant Pyruvate 2 H+ Fumarate Cytochrome b (+3) Dehydroascorbate Ubiquinone (oxidized) Cytochrome c (+3) Fe (+3) ¹/2 0₂ + 2 H+ Reductant Lactate H₂ Succinate Cytochrome b (+2) Ascorbate Ubiquinone (reduced) Cytochrome c (+2) Fe (+2) H₂O Note: E'o is the standard oxidation-reduction poten refers to the partial reaction written as Oxidant + e → reductant. 1 Standard oxidation - reduction potential at pH = 0. Compare with E'o -0.42 at pH = 7. n 2 2 2 1 2 2 1 1 2 E'o (V) -0.19 0.00¹ -0.03 +0.07 +0.08 +0.10 +0.22 +0.77 +0.82 (pH 7, 25°C), and n is the number of electrons transferred. E'o
Transcribed Image Text:TABLE 18.1 Standard reduction potentials of some reactions Oxidant Pyruvate 2 H+ Fumarate Cytochrome b (+3) Dehydroascorbate Ubiquinone (oxidized) Cytochrome c (+3) Fe (+3) ¹/2 0₂ + 2 H+ Reductant Lactate H₂ Succinate Cytochrome b (+2) Ascorbate Ubiquinone (reduced) Cytochrome c (+2) Fe (+2) H₂O Note: E'o is the standard oxidation-reduction poten refers to the partial reaction written as Oxidant + e → reductant. 1 Standard oxidation - reduction potential at pH = 0. Compare with E'o -0.42 at pH = 7. n 2 2 2 1 2 2 1 1 2 E'o (V) -0.19 0.00¹ -0.03 +0.07 +0.08 +0.10 +0.22 +0.77 +0.82 (pH 7, 25°C), and n is the number of electrons transferred. E'o
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