Question

During Citric Acid cycle, the various organic acid undergo decarboxylation. Which of the following organic acids of the above cycle have $4C$, $5C$ and $6C$ respectively?

• A. Pyruvic acid, Malic acid and $\alpha$-Ketoglutaric acid
• B. Pyruvic acid, $\alpha$-Ketoglutaric acid and Citric acid
• C. Oxaloacetic acid, Citric acid and Succinic acid
• D. Succinic acid, $\alpha$-Ketoglutaric acid and citric acid

Answer 1

The Correct Option is D

The Citric Acid Cycle (Krebs cycle) involves several organic acids with different carbon numbers. The key acids with 4, 5, and 6 carbons are:

Succinic acid (4C) - A 4-carbon intermediate formed after the decarboxylation of α-Ketoglutaric acid.

α-Ketoglutaric acid (5C) - A 5-carbon compound that undergoes oxidative decarboxylation to form Succinyl-CoA.

Citric acid (6C) - The 6-carbon compound formed initially by the condensation of oxaloacetate and acetyl-CoA.

Thus, the correct answer is (D) Succinic acid, α-Ketoglutaric acid and Citric acid, as these represent the 4C, 5C, and 6C acids respectively in the Citric Acid Cycle.

Answer 2

The citric acid cycle features organic acids with varying carbon numbers, each playing specific roles. Citric acid, a six-carbon compound, is formed from the condensation of oxaloacetate (4C) and acetyl-CoA (2C). Through decarboxylation, citric acid is converted to α-ketoglutaric acid, a five-carbon molecule, releasing CO₂ and NADH. Further decarboxylation yields succinyl-CoA, which is eventually converted to succinic acid, a four-carbon compound. These intermediates highlight the stepwise breakdown of acetyl-CoA, linking glycolysis to oxidative phosphorylation for ATP production.

Thus, the correct answer is (D) Succinic acid, α-Ketoglutaric acid and Citric acid