Question

During $N_2$ fixation, reduction of one molecule of nitrogen into 2 molecules of $N{H}_3$ consumes ____ molecules of ATP.

• A. 4
• B. 16
• C. 56
• D. 38

Answer 1

The correct option is B 16

Two molecules of ammonia are produced from one molecule of nitrogen gas, at the expense of 16 units of ATP and a supply of electrons and hydrogen ions.

N${}_2$ + 8H+ + 8e${}^{-}$ + 16 ATP = 2NH${}_3$ + H${}_2$ + 16ADP + 16 Pi.

During biological nitrogen fixation, 16 ATP are used. Iron and Molybdenum play important role in this. End product is ammonia and hydrogen.

Thus, the correct answer is '16.'