An alternative electron transfer chain has been identified in Escherichia coli b

Question

An alternative electron transfer chain has been identified in Escherichia coli bacteria that can growth without oxygen. These bacteria express alternate electron transfer chain proteins that form a novel chain. The three main compounds used by this electron transfer chain are summarized in this table as reduction half-reactions with their biological standard state reduction potentials:

1. Order the three compounds in the direction you would expect the electrons to flow in this novel chain (i.e. what is the initial donor, the intermediate carrier, and the terminal acceptor of the electrons). Explain your answer briefly.

Reduction potential Reduction potential half reaction GET in VoltsD Denmethylmenacluindone DMO-t 2e 2HT EDMOHL +0.04 +0.42 NAD+ 2e 2HT NADH+H 0.32

Explanation / Answer

Solution:- More negative is the value of standard reduction potential, more is the tendency to get oxidized. More positive is the standard reduction potential, more is the tendency to get reduced.

In oxidation electrons are given out and in reduction electrons are taken in. If we look at the three given half equations and their standard reduction potentials then for the third equation it is negative means this equation is the initial donor of the electrons.

Value is less positive for first equation it means it would be acting as the intermediate carrier as it could accept electron from third equation and donate to the second equation. Second equation has more positive standard reduction potential so it would be the terminal acceptor of the electrons.

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