Biological Nitrogen Fixation

Reset O₂ level: medium
ATP supply: high

Nitrogenase: the enzyme complex that splits N≡N (944 kJ/mol triple bond). Requires 16 ATP and 8e⁻ per N₂. Irreversibly destroyed by O₂ — leghemoglobin buffers oxygen in the nodule, keeping it near zero while supplying enough for respiration.