Identify the step in the tricarboxylic acid (TCA) cycle which does not involve oxidation of substrate:

Options

1. Succinic acid → Malic acid
2. Succinyl–CoA → Succinic acid
3. Isocitrate → α-ketoglutaric acid
4. Malic acid → Oxaloacetic acid

Correct Answer

Succinyl–CoA → Succinic acid

Explanation

The conversion of Succinyl–CoA to Succinic acid is a substrate-level phosphorylation step that produces GTP. It does not involve oxidation, unlike other steps of the TCA cycle.

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