Question

The process of formation of nitrate from ammonia is known as:

• A. Nitrate assimilation
• B. Nitrification
• C. Ammonia assimilation
• D. Denitrification

Hint:

Nitrification plays a critical role in the nitrogen cycle by converting ammonia into a form that plants can use for growth.

Answer 1

The Correct Option is B

Step 1: Understanding the process.
Nitrification is a two-step process where ammonia (NH₃) is first oxidized to nitrites (NO₂⁻) and then to nitrates (NO₃⁻) by nitrifying bacteria. This process is crucial in the nitrogen cycle, as it makes nitrogen available to plants.
Step 2: Analyzing the options.
(1) Nitrate assimilation: This refers to the process by which plants take up nitrate and convert it into organic nitrogen, but it is not the process of converting ammonia to nitrate.
(2) Nitrification: Correct — Nitrification is the correct process in which ammonia is converted into nitrate through bacterial activity.
(3) Ammonia assimilation: This process refers to the incorporation of ammonia into amino acids and other organic compounds, not the conversion into nitrate.
(4) Denitrification: Denitrification is the process where nitrate is reduced to nitrogen gas, opposite of nitrification.
Step 3: Conclusion.
The correct answer is (2) Nitrification, as it directly involves the conversion of ammonia into nitrate.

Answer 2

The question asks for the specific term used for the biological conversion of ammonia into nitrate, so distinguishing each option by the direction and type of nitrogen transformation it describes identifies the correct term.

1. Nitrate assimilation: This term describes the uptake of nitrate by plants and its conversion into organic nitrogen compounds such as amino acids, which is the opposite end of the process from converting ammonia into nitrate.
2. Nitrification: This term specifically describes the two-step microbial oxidation of ammonia first to nitrite and then to nitrate, carried out by nitrifying bacteria such as Nitrosomonas and Nitrobacter, which is exactly the ammonia-to-nitrate conversion the question describes.
3. Ammonia assimilation: This term refers to the incorporation of ammonia directly into organic molecules like amino acids, a different pathway from oxidising it into nitrate.
4. Denitrification: This term describes the reduction of nitrate back into nitrogen gas, which is the reverse direction of the transformation the question asks about.

Checking the direction of nitrogen transformation in each option shows that only nitrification describes the specific conversion of ammonia into nitrate.

Therefore, the correct answer is Nitrification.