1. The term "coupled redox potential" is defined.

2. The system lactic ion

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pyruvic ion + 2H+ + 2e is shown

to be reversible (when the enzyme is lactic acid dehydrogenase) and its coupled redox potential between pH 5.2 and 7.2 at 32°C. is:

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3. The free energy of the reaction:

lactic ion (1m) → pyruvic ion (1m) = -ΔF = –14,572.

4. The standard free energy of formation (ΔF298) of pyruvic acid (l) is estimated at –108,127. This is merely an approximation as some necessary data are lacking.

5. The importance of coupled redox potentials as a factor in the regulation of the equilibrium of metabolites is indicated.

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