Acetyl CoA forms a 6-C compound after combining with

Options

A. Malic acid
B. Citric acid
C. Succinic acid
D. Oxaloacetic acid.

Answer

To solve the question "Acetyl CoA forms a 6-C compound after combining with," we need to understand the process of how Acetyl CoA interacts with other compounds in cellular respiration, specifically in the Krebs cycle.

### Step-by-Step Solution:

1. **Understanding Acetyl CoA**:
- Acetyl CoA is a 2-carbon molecule that is produced from the breakdown of carbohydrates, fats, and proteins. It plays a crucial role in metabolism.

2. **Krebs Cycle Overview**:
- The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions used by all aerobic organisms to generate energy. It occurs in the mitochondria.

3. **Combining with Oxaloacetic Acid**:
- In the Krebs cycle, Acetyl CoA combines with a 4-carbon compound called oxaloacetic acid.

4. **Formation of Citric Acid**:
- When Acetyl CoA (2 carbons) combines with oxaloacetic acid (4 carbons), they form citric acid (also known as citrate), which is a 6-carbon compound. This reaction is catalyzed by the enzyme citrate synthase.

5. **Conclusion**:
- Therefore, the correct answer to the question is that Acetyl CoA forms a 6-carbon compound (citric acid) after combining with oxaloacetic acid.

### Final Answer:
Acetyl CoA forms a 6-C compound after combining with **oxaloacetic acid**.

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