FAD is electron acceptor in citric acid cycle during the oxidation of

Options

A. Malic acid to oxaloacetatic acid
B. Succinic acid to malic acid
C. Citric acid to `alpha`-ketogulatric acid
D. `alpha`-ketogulatric acid to succinic acid

Answer

To solve the question regarding which reaction in the citric acid cycle involves FAD as an electron acceptor, we will analyze each option provided:

### Step-by-Step Solution:

1. **Understanding the Question**:
The question asks which reaction in the citric acid cycle (Krebs cycle) uses FAD as an electron acceptor.

2. **Reviewing Each Option**:
- **Option A**: Malic acid to oxaloacetic acid.
- This reaction is catalyzed by the enzyme malate dehydrogenase.
- The electron acceptor in this reaction is NAD+, not FAD. Therefore, this option is **incorrect**.

- **Option B**: Succinic acid to fumaric acid.
- This reaction is catalyzed by the enzyme succinate dehydrogenase.
- In this reaction, FAD is the electron acceptor and is reduced to FADH2. Therefore, this option is **correct**.

- **Option C**: Citric acid to alpha-ketoglutaric acid.
- This reaction is catalyzed by isocitrate dehydrogenase.
- The electron acceptor here is NAD+, not FAD. Therefore, this option is **incorrect**.

- **Option D**: Alpha-ketoglutaric acid to succinic acid.
- This reaction is catalyzed by alpha-ketoglutarate dehydrogenase.
- The electron acceptor in this reaction is also NAD+, not FAD. Therefore, this option is **incorrect**.

3. **Conclusion**:
After analyzing all options, we find that the only reaction where FAD acts as an electron acceptor is in **Option B: Succinic acid to fumaric acid**.

### Final Answer:
FAD is the electron acceptor in the citric acid cycle during the oxidation of **succinic acid to fumaric acid**.

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