Question

Nitrogenase requires _____ for its action.
A. Light
B. $M{n^{{2^ + }}}$
C. Super oxygen radicals
D. High input of energy

Answer 1

Nitrogenases are chemicals or enzymes that are produced by certain microbes that reduce nitrogen $({N_2})$ to ammonia $(N{H_3})$. It is very important for the process of nitrogen fixation. They are encoded by the Nif genes.

Complete answer:
As mentioned above, nitrogenase is an enzyme which is involved in nitrogen fixation for the conversion of atmospheric nitrogen to ammonia. Atmospheric nitrogen cannot be used up directly by the plants but ammonia can be taken up. The overall reaction is as follows:
${N_2} + 16ATP + 8{e^ - } + 8{H^ + } \to 2N{H_3} + {H_2} + 16ADP + 16{P_1}$
As we can see from the equation, $16$ $ATP$ molecules are used up for every molecule of nitrogen. $ATP$or adenosine triphosphate is a molecule that provides energy by breaking down to $ADP$or $AMP$. Light, manganese or oxygen radicals are not required by the enzyme to convert nitrogen to ammonia. It needs a high amount of energy in the form of $ATP$. It is said that one molecule of $ATP$has approximately $7300$calories of energy. So, in this process it requires $16$ $ATP$ molecules so that amounts to nearly $116800$calories for one molecule of nitrogen conversion to ammonia.

Hence, the correct answer is option (D).

Note: Leguminous plants have symbiotic association with nitrogen fixing bacteria such as Rhizobia. We can also find free living diazotrophs in the soil which These bacteria are called diazotrophs which means two nitrogen or dinitrogen.
It can be noted that due to the oxidative properties of ${O_2}$, the nitrogenases are inhibited by oxygen irreversibly. So, for that reason nitrogen fixation happens in special sites in the cyanobacteria called heterocysts where oxygen content is very less.