<span>A more efficient and widespread catabolic process, in which oxygen is consumed as a reactant to complete the breakdown of a variety of organic molecules. Similar in broad principle to the combustion of gasoline in an automobile engine after oxygen is mixed with hydrocarbon fuel. Food is the fuel for respiration. The exhaust is carbon dioxide and water. Includes both aerobic and anaerobic processes. However, it originated as a synonym for aerobic respiration because of the relationship of that process to organismal respiration, in which an animal breathes in oxygen.</span>
