Anaerobic respiration

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E. coli use anaerobic respiration

Anaerobic respiration is a form of respiration where elements other than oxygen are used for electron transport. Common replacements for oxygen are nitrates, iron, manganese, sulfates, sulfur, fumaric acid and carbon dioxide. Escherichia coli uses nitrates and fumaric acid for respiration.

For the electron transport chain to function, there must be a final electron acceptor at the end of the chain. This allows electrons to pass through the chain. In aerobic organisms, this final electron acceptor is oxygen. Molecular oxygen is a highly oxidizing agent and so it is an excellent acceptor. In anaerobes, other less-oxidizing substances such as sulfate (SO42−), nitrate (NO3), sulphur (S) are used. These terminal electron acceptors have smaller reduction potentials than O2, so less energy is released per oxidized molecule. Anaerobic respiration is therefore, in general, energetically less efficient than aerobic respiration.

If oxygen is not used at all, the process is called fermentation. Examples of organisms using fermentation are lactic acid bacteria, and yeast. Yeast is a fungi, not bacteria.

The equation for anaerobic respiration is:

  • glucose -> lactic acid (C6H12O6 -> 2C3H6O3)