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Question
Long Answer Question:
Explain biological nitrogen fixation with example.
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Solution
Biological nitrogen fixation:
- It is carried out by prokaryotes called as ‘Nitrogen fixers’ or Diazotrophs’.
- It accounts for nearly 70% of natural nitrogen fixation.
- Nitrogen fixers are either symbiotic or free living.
- 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.
- Azotobacter, Azospirillum is free-living nitrogen-fixing bacteria.
- The cyanobacteria fix a significant amount of nitrogen in specialized cells called heterocysts.
- 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
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