CELLULAR OXIDATION SYSTEMS

Abstract

Discussion of thermodynamics of oxidation-reduction systems, and the types of systems which are of biological importance; these are classified as electromotively active systems, of which the potential is directly measurable; sluggish systems, in which the potential can be measured in the presence of an electro-active system; enzyme-sluggish systems, in which the potential can be measured only in the presence of both the specific enzyme and an electro-active system. The types of systems important biologically include the Fe-porphyrin compounds, of which the cytochrome system is the most important; alloxazines, of which Warburg''s yellow enzyme is the most important; pyridine nucleotides, the C4 di-carboxylic acids, etc. Other potential oxidation-reduction systems, for which no definite function is established, include : ascorbic acid, glutathione, and thiamin. Most mechanisms used by cells involve several intermediate carriers. One type requires the interaction of a sluggish system and an electro-active one; another very commonly used type involves 4 carriers, 2 sluggish and 2 electroactive: pyridine nucleotide, cytochrome-c, alloxazine and cytochrome oxidase.