Question

During nitrogen assimilation in plants, transfer of nitrogen to different amino acids occurs through -

• A. Carboxylation
• B. Oxygenation
• C. Transamination
• D. Transamination

Hint:

Glutamate is the "Main Hub" of nitrogen metabolism.
Transamination is the "Delivery Service" that moves the amino group from the hub to other molecules.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
After plants absorb nitrogen (as nitrate or ammonium) and incorporate it into the first amino acid (usually Glutamate), how is that nitrogen moved to create the diverse set of 20 standard amino acids?
Detailed Explanation:

• Nitrogen Assimilation Steps:
1. Nitrate is reduced to Nitrite, then to Ammonium.
2. Ammonium is incorporated into Glutamate via the GS-GOGAT pathway.

• Transamination:
Once Glutamate is formed, the amino group ($-NH_2$) can be transferred to a variety of keto acids to form new amino acids.
This reaction is catalyzed by aminotransferases (transaminases).
Example: Glutamate + Oxaloacetate $\rightarrow$ $\alpha$-ketoglutarate + Aspartate.
This is the primary way nitrogen is distributed among different amino acids in the cell.

• Analyzing other options:
Nitrification: A soil process where microbes convert ammonium to nitrate.
Carboxylation: The addition of $CO_2$ (e.g., in photosynthesis).

Step 2: Final Answer:
Transamination is the process responsible for transferring nitrogen groups to synthesize different amino acids.