Anaerobic Respiration

Anaerobic respiration is an alternate mode of energy generation in which electron acceptors other than oxygen are used. This mode is a variation of respiration. Because of the analogy to respiration, this process is also classified under the heading of anaerobic respiration. Sulphate, nitrate, carbonate and other organic compounds are the electron acceptors in anaerobic respiration. Although the energy released during electron transport in anaerobic respiration is less, this mode of respiration permits micro organisms to develop in environments where oxygen is absent.

The main difference in anaerobic and aerobic respiration is terminal electron acceptor. In latter case, it is oxygen and in the former type utilizes compounds other than oxygen are used. Prokaryotes include the major part of the organisms carrying out the anaerobic respiration are either organic compounds or organic compounds.

The electron transport system of an-aerobically respiring bacteria contains cytochromes and thus they resemble aerobic bacteria. Certain bacteria are capable of respiring by both the ways- aerobic and anaerobic. However, anaerobic process is favoured only when O₂ is depleted. However, the energy released by oxidation of an electron donor using an electron acceptor other than O₂ is less than if the same compound is oxidized with O₂ as an electron acceptor.

Assimilative and Dissimilative metabolism: Micro organisms use inorganic compounds as nutrient source, energy source or for both the purposes. If they are using these compounds as nutrient source, it is called as Assimilative metabolism. The use of these compounds as electron acceptors for energy metabolism is called Dissimilative metabolism.

Assimilative and Dissimilative metabolism differ markedly. The reduced products in assimilative metabolism are used as building blocks for cell material whereas the reduced products of electron acceptors in dissimilative metabolism are excreted into the environment.