Question

Long Answer Question:

Explain biological nitrogen fixation with example.

Answer 1

Biological nitrogen fixation:

1. It is carried out by prokaryotes called as ‘Nitrogen fixers’ or Diazotrophs’.
2. It accounts for nearly 70% of natural nitrogen fixation.
3. Nitrogen fixers are either symbiotic or free living.
4. Symbiotic N₂ fixation: The best-known nitrogen-fixing symbiotic bacterium is Rhizobium. This soil living/ dwelling bacterium forms root nodules in plants belonging to the family Fabaceae e.g. beans, gram, groundnuts etc.
5. Azotobacter, Azospirillum is free-living nitrogen-fixing bacteria.
6. The cyanobacteria fix a significant amount of nitrogen in specialized cells called heterocysts.
7. Nitrogen fixation is high high-energy-requiring process and nitrogen fixers use 16 molecules of ATP to fix each molecule of nitrogen to form ammonia.

N₂ + 8H⁺ + 8e^- + 16ATP → 2NH₃ + H₂ + 16ADP + 16Pi