Oxidation/Reduction Potential (Molecular Biology)  Many of the
fundamental physiologic reactions in a cell, both in the
metabolic pathways of degradation and in the storage of energy
via production of ATP, involve the transfer of electrons from
one molecule, the donor (or reducing agent), to another, the
acceptor (or oxidant). They are thus called redox reactions and
are catalyzed by redox enzymes.  1. Redox Reactions and Redox
Couples  The molecule donating an electron is the reductant
(red) and becomes oxidized in the reaction, whereas the molecule
accepting the electron is the oxidant (ox) and becomes reduced.
In fact, each redox exchange:   is composed of two reactions:
The reductant and its corresponding oxidized form constitute a
redox couple, in which both partners participate in the redox
reaction. Each redox couple is characterized by a standard
oxidation-reduction potential (pt) that quantitatively defines
its tendency to loose an electron. In a redox reaction, the
redox couple that has the higher