Strategy to Delve into Biochemical Pathways Which Include Oxidation and Reduction Based on the Concept of Total Carbon Oxidation Number of Biomolecules

Abstract

Biochemistry students at the introductory level easily comprehend the importance of energy-yielding oxidation and reduction biochemical processes, but nevertheless, they fight with words “oxidation” and “reduction” (and with the corresponding adjectives, “oxidized” and “reduced”) applied in biochemistry textbooks to describe metabolic reactions. This is because, in general, comparison of biomolecules, of different atomic composition and bonding sequence, based on the oxidation state of individual atoms does not make it immediately apparent whether oxidation or reduction occurs in a metabolic step, or which one of the two biomolecules of a redox couple must be considered the oxidized and which one is the reduced form of the couple. Here we present a general and simple strategy, called TCON (total carbon oxidation number) strategy, which allows one to rationalize the use of the words oxidation and reduction in biochemistry. Application of the TCON strategy to compare any pair of biomolecules, or to analyze biochemical conversions, makes available an indicator number which unambiguously indicates whether oxidation or reduction is the correct word to be used. Examples are presented which demonstrate that the TCON strategy may provide a more satisfying understanding of metabolic pathways by exposing subtle chemical relations which exist between the assortment of metabolites participating in a biochemical pathway.