In theory how many protons could be pumped under standard state conditions by Complex III per mol of CoQ oxidized,considering the following information? (NOTE: mt = mitochondria) Coenzyme Q + 2H⁺ + 2 e^- → coenzyme QH₂ $\varepsilon$^o ' ≈ 0.040 V Cytochrome c (Fe³⁺)+ e^- → cytochrome c (Fe²⁺)$\varepsilon$^o' ≈ 0.270 V H⁺ (outside mt)→ H⁺ (inside mt)∆G ≈ -20kJ/mol Faraday constant (F)≈ 100 kJ/Vmol ∆Gº' = -nF∆E₀' A)four or less protons B)greater than four protons but less than or equal to six protons C)greater than six protons but less than or equal to eight protons D)greater than 8 protons E)Cannot be determined from the information provided.

Question

Quizplus · Accepted Answer

The number of protons pumped by Complex III per mole of CoQ oxidized can be estimated using the given standard reduction potentials and the Gibbs free energy change for proton translocation. The difference in standard reduction potentials between cytochrome c and CoQ is 0.270 V - 0.040 V = 0.230 V. Using the equation ∆Gº' = -nF∆Eº', where n is the number of electrons (2 in this case), F is the Faraday constant (100 kJ/Vmol), and ∆Eº' is the difference in standard reduction potentials, we can calculate the Gibbs free energy change for the electron transfer process. Substituting the values, we get ∆Gº' = -2 * 100 kJ/Vmol * 0.230 V = -46 kJ/mol. Given that the translocation of one proton across the mitochondrial membrane has a Gibbs free energy change of about -20 kJ/mol, approximately 46 kJ / 20 kJ/mol ≈ 2.3 protons could be translocated per electron, or about 4.6 protons per two electrons. Therefore, the correct answer is that greater than four protons but less than or equal to six protons could be pumped by Complex III per mole of CoQ oxidized.

In Theory How Many Protons Could Be Pumped Under Standard ε\varepsilonε

In Theory How Many Protons Could Be Pumped Under Standard $\varepsilon$