Question

The first decarboxylation reaction during Krebs cycle occurs in which of the following intermediates?

• A. Isocitrate
• B. Succinate
• C. Oxalosuccinate
• D. α - ketoglutarate

Hint:

In the Krebs cycle, the first decarboxylation reaction involves the conversion of isocitrate to α-ketoglutarate via oxalosuccinate.

Answer 1

The Correct Option is C

Step 1: Understanding the Krebs cycle.
The Krebs cycle is a critical metabolic pathway that involves decarboxylation reactions. The first decarboxylation reaction in the cycle occurs when isocitrate is converted to α-ketoglutarate through an intermediate known as oxalosuccinate.
Step 2: Analyzing the options.
(A) Isocitrate: Incorrect — The decarboxylation reaction does not occur at isocitrate; it is a precursor in the cycle.
(B) Succinate: Incorrect — Succinate is involved in the reduction step of the cycle, not decarboxylation.
(C) Oxalosuccinate: Correct — Oxalosuccinate is the intermediate where the first decarboxylation occurs in the Krebs cycle.
(D) α - ketoglutarate: Incorrect — α-ketoglutarate is formed after the decarboxylation of oxalosuccinate, not before.
Step 3: Conclusion.
The correct answer is (C) Oxalosuccinate, as it is the intermediate in which the first decarboxylation occurs in the Krebs cycle.