Question

The amino donor to oxoglutarate during photorespiration is:

• A. Glycine
• B. Glutamate
• C. Serine
• D. Aspartate

Hint:

The transamination reaction in the peroxisome is: \[ \text{Glyoxylate} + \text{Glutamate} \to \text{Glycine} + \alpha\text{-ketoglutarate} \] This shows that glutamate donates its amino group, leaving oxoglutarate as the product.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Photorespiration involves the recycling of 2-phosphoglycolate through several transamination reactions that transfer amino groups between different intermediates.

Step 2: Detailed Explanation:
In the peroxisome, glyoxylate is converted to glycine.
This transamination is catalyzed by glutamate-glyoxylate aminotransferase.
In this reaction, Glutamate acts as the amino donor, transferring its amino group to glyoxylate to produce Glycine and $\alpha$-ketoglutarate ($\alpha$-oxoglutarate).
This maintains the nitrogen balance of the cycle and links the peroxisomal reactions to the nitrogen re-assimilation pathway in the chloroplast.

Step 3: Final Answer:
Glutamate serves as the primary amino donor that yields oxoglutarate during the transamination step in photorespiration.