Question

XXXXXX (31 points total) A scientist in New York has asked his graduate student to consider the flow of electrons for the reduction of a total of 4 O₂ molecules by electrons from reduced Coenzyme Q (also called “ubiquinone”). This student has contacted you for help, since you are an expert on this topic.

A). (8 pts) Write the two half reactions you will use (with the correct stoichiometry) and their corresponding reduction potential values.

ANSWER:

B). (6 pts) Calculate the free energy (DG) released by this reaction. Faraday’s constant F = 96.5 kJ/V*mol. No need to calculate the math, just make sure all the numbers needed are present in the final answer.

ANSWER:

C). (9 pts) The algae that this graduate student is working with, though, does not have proton wires as part of their complexes in the ETC. How does this affect the system and what is the direct and indirect result of this strange mutation on the algae? (50 words total)

ANSWER:

D). (8 points) This strange algae also has fewer available Cytochrome c molecules than the normal ETC system. What is limitation this imposes on the ETC and energy production? (30 words max)

ANSWER:

Answer 1

Answer A:)

The electron transport chain has following two half-chemical reactions:

NADH + H+ = 2H+ + NAD+ + 2e- Electric potential, εoxidation = 0.32V

(1/2) O2 + 2e- + 2H+ = H2O Electric potential, εreduction = 0.82 V

There are total 4 O2 molecules are reduced. Therefore, multiply each reaction by 4.

4NADH + 4H+ = 4NAD+ + 8H+ + 8e- Reduction potential, εoxidation = 1.28 V

2O2 + 8H+ + 8e- = 4H2O Reduction potential, εoxidation = 3.28 V

The overall reaction is below:

4NADH + 4H+ + 2O2 = 4NAD+ + 4H2O, εredox = 4.56 V

Answer B:)

Calculate free energy by using the following formula:

ΔG = -nFε

n is the change of number of electrons. Here n = 8

ΔG = - 8 x 96.5 x 4.56

ΔG = - 3520.32 kJ

Answer C:)

If the algae do not have proton wires, the mitochondria cannot cause H+ potential pump, which is essential to drive electrons.

Answer D:)

Fewer Cytochrome c molecules will transfer a low amount of electrons in comparison to normal cells. It will cause lesser production of ATPs.

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