Question

In the TCA cycle, GTP is formed during which of these reactions:

• A. Citric acid $\to$ alpha-ketoglutaric acid
• B. Malic acid $\to$ oxalo-acetic acid
• C. alpha-ketoglutaric acid $\to$ Succinyl $CoA$
• D. Succinyl- $CoA\to$ Succinic acid

Answer 1

Answer: (D)

In TCA cycle, oxaloacetic acid along with water undergoes condensation to form citric acid in the presence of citrate synthase which is then followed by its isomerization into isocitrate. This further undergoes decarboxylation twice to form alpha-ketoglutaric acid and then succinyl-CoA. Succinyl- CoA is then converted to succinic acid and a molecule of GTP is released. This forms the substrate level of phosphorylation.