Name the compound which attaches to acetyl CoA to form the first stable compound during citric acid cycle?

Options

A. Oxaloacetate
B. Acetyl CoA
C. Citric acid
D. Pyruvic acid

Answer

To answer the question about the compound that attaches to acetyl CoA to form the first stable compound during the citric acid cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Citric Acid Cycle**: The citric acid cycle (also known as the Krebs cycle or TCA cycle) is a series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA.

2. **Identifying Acetyl CoA**: Acetyl CoA is a two-carbon molecule that is derived from the breakdown of carbohydrates, fats, and proteins. It is a key substrate in the citric acid cycle.

3. **Recognizing the Need for a Four-Carbon Compound**: To form the first stable compound in the citric acid cycle, acetyl CoA (2 carbons) must combine with a four-carbon compound. This will result in a six-carbon compound.

4. **Identifying the Four-Carbon Compound**: The four-carbon compound that combines with acetyl CoA is oxaloacetate. Oxaloacetate is a key intermediate in the citric acid cycle.

5. **Formation of Citrate**: When acetyl CoA combines with oxaloacetate, they form citrate (or citric acid), which is a six-carbon compound. This reaction is catalyzed by the enzyme citrate synthase.

6. **Conclusion**: Therefore, the compound that attaches to acetyl CoA to form the first stable compound during the citric acid cycle is **oxaloacetate**.

### Final Answer:
The compound that attaches to acetyl CoA to form the first stable compound during the citric acid cycle is **oxaloacetate**.

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