Biological Nitrogen Fixation

Biological Nitrogen Fixation

Biological Nitrogen Fixation - Under agricultural conditions, the nitrogen removed is usually greater than the nitrogen input. To maintain fertility, nitrogen must be returned to the soil.

This takes place mainly by biological nitrogen fixation, which is responsible for the major reduction of dinitrogen to ammonia that is used by plants (and there by indirectly by animals).

Nitrogen fixation is an energy consuming process. It requires (i) 6e- from a low potential reductant, such as reduced ferredoxin and (ii) at least four ATP molecules, which are involved in the reduction of N₂to 2NH₃ .

In the presence of a source of electrons and ATP, the enzyme nitrogenase becomes a powerful reducing agent, and catalyzes the six electron reduction of N₂to 2NH₃.

6H⁺+6e^-+N₂ -->2NH₃ .

The ATP must be supplied continuously by an ATP generating system. Nitrogenase is inhibited by high concentrations of ATP. Another striking feature of the nitrogenase system is that it is extremely sensitive to even low concentrations of oxygen, and is irreversibly in activated.

Biological nitrogen fixation is much more efficient than the man, made processes. The industrial processes require rather drastic conditions of temperature and pressure. In contrast, microorganisms fix atmospheric nitrogen very smoothly at a temperature of 20°C and atmospheric pressure of one.

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