Before combining with OAA, pyruvic acid is changed into

Options

A. Succinic acid
B. Malic acid
C. Acetyl CoA
D. Citric acid.

Answer

To answer the question "Before combining with OAA, pyruvic acid is changed into," we need to understand the process that occurs after glycolysis, where pyruvic acid is produced. Here’s a step-by-step explanation:

### Step-by-Step Solution:

1. **Glycolysis Overview**:
- Glycolysis is the metabolic pathway that converts glucose into pyruvic acid. This process occurs in the cytoplasm of the cell and produces a net gain of 2 ATP molecules and 2 NADH molecules.

2. **Conversion of Pyruvic Acid**:
- Before pyruvic acid can enter the citric acid cycle (Krebs cycle), it must be converted into another compound. This conversion is crucial for its entry into the cycle.

3. **Formation of Acetyl Coenzyme A**:
- The enzyme responsible for this conversion is called **pyruvate dehydrogenase**. It catalyzes the reaction that transforms pyruvic acid into **acetyl coenzyme A (acetyl CoA)**.
- During this conversion, one molecule of carbon dioxide (CO2) is released, and one molecule of NADH is produced.

4. **Characteristics of Acetyl CoA**:
- Acetyl CoA is a 2-carbon molecule. It is important because it can then combine with oxaloacetic acid (OAA), which is a 4-carbon compound, to form citrate (a 6-carbon compound) in the citric acid cycle.

5. **Conclusion**:
- Therefore, before pyruvic acid combines with oxaloacetic acid, it is changed into **acetyl coenzyme A**.

### Final Answer:
Before combining with OAA, pyruvic acid is changed into **acetyl coenzyme A**.