Briefly describe the mechanism of nitrogen fixation.
GeneralClass 12AllAnswered 27 Mar 2026
Answer
Answer:
Nitrogen fixation is catalyzed by the enzyme nitrogenase under anaerobic conditions:
Steps:
- Substrate Binding: A nitrogen molecule (N₂) binds to the Mo-Fe component of nitrogenase.
- Reduction: The N≡N triple bond is sequentially reduced by addition of hydrogen atoms supplied by NADPH.
- Intermediate Formation: Progressive reduction produces:
- Dimide (N₂H₂)
- Hydrazine (N₂H₄)
- Ammonia (NH₃)
- Product Release: Free nitrogenase enzyme is regenerated and can bind another N₂ molecule.
Overall Reaction:N₂ + 8e⁻ + 8H⁺ + 16ATP → 2NH₃ + H₂ + 16ADP + 16Pᵢ
This highly energy-intensive process requires 16 ATP molecules per N₂ fixed.
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