Energy production in anaerobic organisms

Biological redox processes are required for the synthesis of “energy-rich” compounds which are in an enzyme-controlled equilibrium with the general energy carrier adenosine triphosphate (ATP). The basic mechanisms of biological energy transformation are substrate level (SLP) and electron transport phosphorylations (ETP). In anaerobic catabolism the numerous nutrients are channelled into only a few substrate level phosphorylations; the occurrence in chemotrophic anaerobes of energy conservation coupled to electron transport has not yet been demonstrated unequivocally. At present, the determination of the ATP turnover (Y_ATP) in growing cells appears to be a promising method of approaching this problem. The existing knowledge of oxygen dependent enzyme reactions and their molecular evolution provides the basis for a biochemical definition of aerobic and anaerobic organisms.