Anaerobic Respiration

Anaerobic Respiration | The breakdown of glucose in the absence of oxygen to yield chemical energy.

Anaerobic respiration is a type of cellular respiration in which foods (primarily carbohydrates), are partially oxidised releasing chemical energy. Since the substrates are not completely oxidised only approximately 5 - 6% of ATP is produced in comparison to aerobic respiration (which requires oxygen).

Anaerobic respiration occurs in some bacteria, plants and yeasts and in muscle tissue when there is an absence of oxygen (see oxygen debt).

In plants and microorganism the pyruvate from glycolysis is converted to ethanol and carbon dioxide (see alcoholic fermentation). In animals however, pyruvate is converted to lactic acid.

Organisms may be classified based upon their ability utilise oxygen for respiration, e.g.
Obligate anaerobes are organisms that cannot use free oxygen for respiration, in fact oxygen may be toxic inhibiting growth or causing death for these organisms.

Facultative anaerobes are organisms such as bacteria and fungi that are able to alter their metabolism in response to available oxygen. Thus, such organisms can respire in the presence of oxygen or absence of it.