FAD participates in Krebs' cycle as electron acceptor during conversion of

Options

A. succinly CoA to succinic acid
B. `alpha`-ketoglutarate to succinly CoA
C. succinic acid to fumaric acid
D. fumaric acid to malic acid

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of FAD in the Krebs Cycle:**
- FAD (Flavin Adenine Dinucleotide) acts as an electron acceptor in various biochemical reactions, particularly in the Krebs cycle (also known as the citric acid cycle).

2. **Identifying the Relevant Reactions:**
- The question provides four options regarding conversions that occur in the Krebs cycle:
1. Succinyl coenzyme A to succinic acid
2. Alpha-ketoglutarate to succinyl coenzyme A
3. Succinic acid to fumaric acid
4. Fumaric acid to malic acid

3. **Analyzing Each Option:**
- **Option 1:** Succinyl coenzyme A to succinic acid - This reaction involves the formation of GTP (or ATP) and does not involve FAD.
- **Option 2:** Alpha-ketoglutarate to succinyl coenzyme A - This reaction results in the formation of NADH, not FADH2.
- **Option 3:** Succinic acid to fumaric acid - This reaction is catalyzed by the enzyme succinate dehydrogenase and involves the reduction of FAD to FADH2, making FAD the electron acceptor.
- **Option 4:** Fumaric acid to malic acid - This reaction involves the addition of water (hydration) and does not involve FAD.

4. **Conclusion:**
- The correct answer is **Option 3: Succinic acid to fumaric acid**, where FAD participates as an electron acceptor.