Question

Identify the step in tricarboxylic acid cycle, which does not involve oxidation of substrate.

Options

• Succinyl-CoA → Succinic acid

• Isocitrate → a-ketoglutaric acid

• Malic acid → Oxaloacetic acid

• Succinic acid → Malic acid

Answer 1

Succinyl-CoA → Succinic acid

Explanation:

The substrate is not oxidised during the conversion of succinyl-CoA to succinic acid in the tricarboxylic acid (TCA) cycle. Rather, this phase releases Coenzyme A (CoA) and converts succinyl-CoA to succinate. The conversion of isocitrate to a-ketoglutaric acid and a-ketoglutaric acid to succinyl-CoA involves the oxidation stages in the TCA cycle.