Question

How many molecules of ATP are required to fix one molecule of nitrogen?

• A. 12
• B. 20
• C. 6
• D. 16

Hint:

Nitrogen fixation is a crucial process for converting atmospheric nitrogen into forms that plants can use for growth, and it is an ATP-consuming process.

Answer 1

The Correct Option is D

The process of nitrogen fixation, where atmospheric nitrogen (N₂) is converted into ammonia (NH₃), requires energy input. The enzyme nitrogenase catalyzes this process, and it requires 16 ATP molecules for the conversion of one molecule of nitrogen into ammonia.

(1) 16 ATP Molecules:
- Nitrogen fixation is an energy-intensive process. In addition to ATP, the enzyme nitrogenase also requires electrons (often provided by ferredoxin) to convert nitrogen gas into a usable form for plants. 16 ATP molecules are consumed for every nitrogen molecule fixed.

(2) Why Other Options Are Incorrect:
- 12 ATP (Option 1) and 6 ATP (Option 3) are not sufficient for the entire nitrogen fixation process.
- 20 ATP (Option 2) is higher than the actual requirement of 16 ATP molecules for the fixation of one nitrogen molecule.

Conclusion: It takes 16 ATP molecules to fix one molecule of nitrogen into ammonia.