In Kreb's cycle, the first product is citric acid which is a 6-carbon compound. It is foirmed by a condensing irreversible reaction between -

Options

A. OAA and Pyruvic acid
B. OAA and Acetyl Coenzyme A
C. Pyruvic acid and Acetyl Coenzyme A
D. OAA and Citrate synthetase

Answer

**Step-by-Step Solution:**

1. **Understanding the Kreb's Cycle**: The Kreb's cycle, also known as the citric acid cycle or TCA cycle, is a crucial metabolic pathway that plays a key role in cellular respiration. The cycle begins with the formation of citric acid.

2. **Identifying the Reactants**: The first product of the Kreb's cycle is citric acid, which is a 6-carbon compound. To form citric acid, two specific molecules must combine: oxaloacetic acid and acetyl Coenzyme A.

3. **Analyzing the Components**:
- **Oxaloacetic Acid**: This is a 4-carbon compound.
- **Acetyl Coenzyme A**: This is a 2-carbon compound derived from the breakdown of carbohydrates, fats, and proteins.

4. **Combining the Reactants**: When oxaloacetic acid (4 carbons) combines with acetyl Coenzyme A (2 carbons), they undergo a condensation reaction to form citric acid (6 carbons). This reaction is irreversible and is a key step in the Kreb's cycle.

5. **Conclusion**: Therefore, the first product of the Kreb's cycle, citric acid, is formed by the condensation of oxaloacetic acid and acetyl Coenzyme A.

**Final Answer**: Citric acid is formed by the condensation of oxaloacetic acid (4 carbons) and acetyl Coenzyme A (2 carbons).

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