In glycolysis during which reaction, water molecule is released

Options

A. 2-Phosphoglyceric acid `rarr` Phosphoenol pyruvic acid
B. PGAL `rarr` 3PGA
C. 1,3-biphosphoglyceric acid `rarr` Phosphoglyceric acid
D. Phosphoenol pyruvic acid `rarr` Pyruvic acid.

Answer

To determine during which reaction in glycolysis a water molecule is released, we can analyze the options provided:

1. **Identify the reactions in glycolysis**:
- The glycolysis pathway consists of several steps, and we need to focus on the specific reactions mentioned in the options.

2. **Examine each option**:
- **Option 1**: 2-phosphoglyceric acid to phosphoenolpyruvic acid
- **Option 2**: Phosphoglyceraldehyde to 3-phosphoglyceric acid
- **Option 3**: 1,3-bisphosphoglyceric acid to phosphoglyceric acid
- **Option 4**: Phosphoenolpyruvic acid to pyruvic acid

3. **Analyze the first option**:
- The conversion of 2-phosphoglyceric acid to phosphoenolpyruvic acid is catalyzed by the enzyme enolase. During this reaction, a water molecule (H2O) is released.

4. **Analyze the other options**:
- **Option 2**: The conversion of phosphoglyceraldehyde to 3-phosphoglyceric acid does not involve the release of water.
- **Option 3**: The conversion of 1,3-bisphosphoglyceric acid to phosphoglyceric acid also does not involve the release of water.
- **Option 4**: The conversion of phosphoenolpyruvic acid to pyruvic acid does not release water either.

5. **Conclusion**:
- The only reaction in glycolysis where a water molecule is released is the conversion of 2-phosphoglyceric acid to phosphoenolpyruvic acid.

Thus, the correct answer is:
**2-phosphoglyceric acid to phosphoenolpyruvic acid**.