anaerobic respiration A type of respiration in which foodstuffs (usually carbohydrates) are partially oxidized, with the release of chemical energy, in a process not involving atmospheric oxygen. Since the substrate is never completely oxidized the energy yield of this type of respiration is lower than that of aerobic respiration. It occurs in some yeasts and bacteria and in muscle tissue when oxygen is absent (see oxygen debt). Obligate anaerobes are organisms that cannot use free oxygen for respiration; facultative anaerobes are normally aerobic but can respire anaerobically during periods of oxygen shortage. Alcoholic fermentation is a type of anaerobic respiration in which one of the end products is ethanol.

anaerobic respiration n. a type of cellular respiration in which foodstuffs (usually carbohydrates) are never completely oxidized because molecular oxygen is not used.