Q.Write the role of nitrogenase enzyme in nitrogen fixation.

Nitrogenase catalyses the ATP-dependent reduction of atmospheric N2 gas to ammonia (NH3) — the single reaction at the heart of biological nitrogen fixation — and it is extremely oxygen-sensitive, so nitrogen-fixing systems must protect it from O2.

Atmospheric nitrogen (N2) is chemically very stable due to its strong triple covalent bond, and most organisms cannot use it directly. Certain prokaryotes (e.g. the symbiotic bacterium Rhizobium in legume root nodules, and free-living organisms like Azotobacter, Cyanobacteria) possess the enzyme nitrogenase, which is able to break this triple bond and reduce N2 to ammonia:

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

Key features of nitrogenase's role:

1. It is a Molybdenum-Iron (Mo-Fe) protein complex that catalyses this reduction.
2. The reaction is highly energy-demanding, consuming a large amount of ATP (roughly 16 ATP per N2 molecule reduced). …