Anaerobic respiration is defined as the respiration, which uses electron acceptors other than molecular oxygen. It is true that in this kind of kind of respiration, is not the final electron acceptor, however, the entire process utilises respiratory electron transport chain. The entire process of anaerobic respiration, the electrons become shuttled to an electron transport chain, and the final electron acceptor is Oxygen. Molecular Oxygen is a highly oxidizing agent. This is the reason for which oxygen is referred as the best electron acceptor. In this kind of respiration, the substances, which are less –oxidizing such as Nitrate (NO3−), Fumarate, Sulphate (SO42−), or Sulphur (S) are used. These substances hold the ability to reduce less molecule than that of the molecule. Therefore, anaerobic respiration is less efficient than aerobic. Anaerobic respiration is one of the most essential components of global nitrogen, iron, sulfur, and carbon cycles through the reduction of the oxyanions of nitrogen, sulfur, and carbon to more-reduced compounds.
These compounds are highly dependent on anaerobic respiration, which can have a major impact on global warming and carbon cycle. Anaerobic respiration can happen in different environment such as freshwater and marine sediments, soil, subsurface aquifers, deep subsurface environments, and biofilms. In addition, in the soil which contain oxygen, can also be referred as the micro-environment which lack oxygen for slow diffusion, which is referred as oxygen gas. Anaerobic respiration is the matter of utmost importance in order to maintain ecological balance. Usage of nitrate as a terminal electron acceptor, or dissimulator DE nitrification is one of the major instances of ecological importance of anaerobic respiration. This is the main route, through which nitro Zane used to return to the environment, molecular nitrogen gas. Another major example of ecological importance of anaerobic respiration is methanogens, one of the major forms of carbonate respiration which is widely used in order to produce methane gas by anaerobic digestion.
Without the presence of oxygen, the electron transport chain (ETC) cannot continue as there is no terminal electron acceptor. Therefore the usual number of ATP molecules cannot be created. Cessation of the ETC leads to reduced activity of the reactions before this step, such as the Krebs cycle and glycolysis. The anaerobic pathway utilises pyruvate, the final product of glycolysis. Some of the major instances of anaerobic respirations are fermentation of alcohol and lactic acid and their decomposition within the organic matter. In addition to that, some of the vital prokaryotes like bacteria and archaea, which are used to live in low oxygen environment, are highly dependent on anaerobic respiration in order to break down the fuel. For example, some archaea called methanogens can use carbon dioxide as a terminal electron acceptor, producing methane as a by-product. The chemical equation in chemistry is as follows:
C6H12O6 + 6O2 → 6CO2 + 6H2O (glucose + oxygen -> carbon dioxide + water).
This kind of respiration also hold the ability to produce energy and uses glucose. However, the rate of energy, produced by anaerobic respiration is low and this does not require any oxygen.