Pyruvic acid before combining with the oxaloacetic acid of Krebs cycle becomes

Options

A. Citric acid
B. Acetoacetic acid
C. Cis-aconitic acid
D. Acetyl CoA

Answer

### Step-by-Step Solution:

1. **Understanding Pyruvic Acid**:
- Pyruvic acid is a 3-carbon compound that is the end product of glycolysis. Glycolysis is the process that breaks down glucose into pyruvate, which is then converted into pyruvic acid.

2. **Entry into Krebs Cycle**:
- Before pyruvic acid can enter the Krebs cycle (also known as the citric acid cycle), it must undergo a transformation.

3. **Decarboxylation Process**:
- The first step after pyruvic acid enters the mitochondria is decarboxylation. This process involves the removal of a carbon atom from pyruvic acid, which releases carbon dioxide (CO₂).

4. **Formation of Acetyl Coenzyme A**:
- After decarboxylation, the remaining 2-carbon compound is known as acetyl coenzyme A (acetyl CoA). This is a crucial intermediate that enters the Krebs cycle.

5. **Combination with Oxaloacetic Acid**:
- Acetyl CoA then combines with oxaloacetic acid (a 4-carbon compound) to form citric acid (a 6-carbon compound), which is the first step of the Krebs cycle.

6. **Conclusion**:
- Therefore, before combining with oxaloacetic acid in the Krebs cycle, pyruvic acid becomes acetyl coenzyme A.

### Final Answer:
**Pyruvic acid before combining with the oxaloacetic acid of the Krebs cycle becomes acetyl coenzyme A.**

---