How ammonia is formed in human body?

Formation of Ammonia.

Oxidative transdeamination is the combination of three processes called transamination, deamination and oxidation. The amino acids which enter the body of the animal through diet are catabolised through this process. The whole process is catalyzed by enzymes transaminases and dehydrogenases.

The whole process takes place in the following steps:

  • The first step involves the conversion of aspartic acid into oxaloacetic acid. In this process, the amino group of the aspartic acid is transferred to alpha-ketoglutaric acid converting it into glutamic acid.
  • The next step involves the removal of ammonia from the glutamic acid by converting it into alpha-ketoglutaric acid along with the oxidation process. In the simultaneous oxidation reaction, there is a removal of a pair of hydrogen atoms from glutamic acid. The whole process is called transamination.
  • The hydrogen atoms produced by the oxidation of glutamic acid reduces NAD into NADH and H+.
  • The NADH and the oxaloacetic acid produced are oxidized in the mitochondria to CO2 and H2O generating ATP in the process.

Ammonia is toxic to cells for the following reasons :

  • If allowed to accumulate, ammonia would raise the pH in cells to toxic levels can affect the metabolism adversely.
  • It replaces alpha-ketoglutarate from Kreb Cycle and NADH from the electron transfer system due to which the cellular concentrations of ATP get lowered.
  • Some of the Ammonium salts prevents the active transport of ions through membranes.

Therefore, animals need to get rid of the toxic ammonia through excretion or it must be converted into a less toxic form (detoxification) as soon as it is formed.

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