# DBT JRF 2022 — Question 14

Exam: DBT JRF 2022 · Section: A · Topic: Biochemistry › Acetyl-CoA Metabolism · Difficulty: Medium

## Question

Which one of the following compound(s) is/are NOT the carbon source of acetyl Co-A?

## Options

- **A.** Ethanol
- **B.** Valine/isoleucine
- **C.** Pyruvate
- **D.** Oxaloacetate/acetoacetate

## Answer

Option D

## Explanation

Carbon sources for Acetyl-CoA: Acetyl-CoA can be generated from: • Ethanol → Acetaldehyde → Acetate → Acetyl-CoA • Pyruvate → Acetyl-CoA (via pyruvate dehydrogenase complex; losing one CO₂) • Valine and Isoleucine (branched-chain amino acids): partially ketogenic, catabolised to propionyl-CoA and acetyl-CoA • Acetoacetate (a ketone body): converted to 2 Acetyl-CoA via thiolase NOT a carbon source for Acetyl-CoA: • Oxaloacetate (OAA): a 4-carbon TCA cycle intermediate that is glucogenic — it CANNOT be converted to Acetyl-CoA (no enzyme catalyses OAA → Acetyl-CoA directly). Answer: Oxaloacetate/acetoacetate (Option 4) — specifically oxaloacetate is the one NOT a carbon source.

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