Question

The first stable compound of C4 pathway is ................

• A. phosphoglyceric acid
• B. 1, 3 diphosphoglyceric acid
• C. oxalosuccinic acid
• D. oxaloacetic acid

Hint:

In C4 plants, oxaloacetic acid is formed as the first stable compound during carbon fixation, before being converted into other molecules.

Answer 1

The Correct Option is D

Step 1: Understanding C4 pathway.
The C4 pathway of photosynthesis is an alternative carbon fixation pathway found in certain plants, which helps in reducing photorespiration. The first stable compound formed in the C4 pathway is oxaloacetic acid (OAA).
Step 2: Analyzing the options.
(A) phosphoglyceric acid: This is the first stable compound in the C3 pathway, not the C4 pathway.
(B) 1, 3 diphosphoglyceric acid: This is also related to the C3 pathway, specifically in the Calvin cycle.
(C) oxalosuccinic acid: This is not the correct compound in the C4 pathway.
(D) oxaloacetic acid: Correct — Oxaloacetic acid (OAA) is the first stable compound in the C4 pathway, formed after CO2 is fixed into a 4-carbon molecule.
Step 3: Conclusion.
The correct answer is (D) oxaloacetic acid, as it is the first stable compound in the C4 pathway.