MCAT Question A Day - 5/2/14 - Answer!

As electrons move within the electron transport chain, each intermediate carrier molecule is:

A. oxidized by the preceding molecules and reduced by the following molecule.

B. reduced by the preceding molecule and oxidized by the following molecule.

C. reduced by both the preceding and the following molecules.

D. oxidized by both the preceding and the following molecules.

B is correct. As electrons flow, the carriers pass along one or two electrons, and are reduced (gain electrons) then oxidized (lose electrons) until the last carrier donates electrons to oxygen.

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