The first stable compound of Krebs cycle is

Options

A. Acetyl CoA
B. Citric acid
C. Oxaloacetic acid
D. Fumaric acid.

Answer

To determine the first stable compound of the Krebs cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the citric acid cycle or tricarboxylic acid (TCA) cycle, is a key metabolic pathway that plays a crucial role in aerobic respiration.

2. **Starting Components**: The cycle begins with the combination of acetyl-CoA, which is derived from carbohydrates, fats, and proteins, and oxaloacetic acid (OAA).

3. **Formation of Citric Acid**: When acetyl-CoA combines with oxaloacetic acid, a condensation reaction occurs. This reaction also involves the addition of water. The result of this reaction is the formation of citric acid (also known as citrate).

4. **Identifying the First Stable Compound**: Citric acid is a 6-carbon compound formed as the first stable product of the Krebs cycle. It is crucial to note that this is the first compound that is formed after the initial reaction.

5. **Enzyme Involvement**: The enzyme responsible for catalyzing the reaction that forms citric acid from acetyl-CoA and oxaloacetic acid is called citrate synthase.

6. **Conclusion**: Therefore, the first stable compound of the Krebs cycle is citric acid.

### Final Answer:
The first stable compound of the Krebs cycle is **citric acid**.

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