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Nitrogen Metabolism

Nitrogen Metabolism

  • The process of conversion of inert nitrogen into utilization compound of nitrogen like nitrate ammonia etc. is termed as nitrogen fixation.

                                            Figure: Nitrogen cycle

1 Nodule Formation

  • Biological nitrogen fixation is performed by bacteria and cyanobacteria.
  • A most common example of symbiotic N2 fixing associated is a legume-bacteria relationship. Species of Rhizobium bacteria are associated with the roots of the leguminous plant of family Fabaceae.

                                                  Figure: Root nodule

  • In the process of biological nitrogen fixation by free-living and symbolic nitrogen fixers, the dinitrogen molecule (N≡N) is progressively reduced step by step to ammonia (NH3) by the addition of parts of hydrogen atoms.

 

  •  The overall biochemical reaction of biological N2 – fixation is as follows

Reaction Synthesis of amino acids: amino acids are organic compounds of nitrogen assimilation, they are synthesized by:

2 Reductive ammonium

 The ammonium formed by nitrogen assimilation (i.e., reduction of nitrates) reacts with α-ketoglutaric acid from the amino acid-glutamic acid. The reaction occurs in the presence of enzyme glutamate dehydrogenase.

 3 Transamination

It is a transfer of the amino group of one amino acid with the keto group of a keto acid. The enzyme required is transaminase or aminotransferase.

  • The amino acids produced from the above-mentioned processes form amino acid chains or polypeptide over ribosomes during the processes of translation of genetic code carried by mRNAs. Polypeptide gives rise to protein, which is utilized by the plants.

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