In which of the following reaction of glycolysis, a molecule of water is removed from the substrate

Options

A. Fructose-6-phosphate `rarr` Fructose-1, 6-bisphosphate
B. 3-phosphate-glyceraldehyde`rarr` 1, 3 bisphosphoglyceric acid
C. PEP `rarr` Pyruvic acid
D. 2- phosphoglycerate `rarr`PEP

Answer

To determine which reaction in glycolysis involves the removal of a water molecule from the substrate, we can analyze the options provided and identify the specific reaction where dehydration occurs.

### Step-by-Step Solution:

1. **Understanding Glycolysis**: Glycolysis is a series of enzymatic reactions that convert glucose into pyruvate, producing ATP and NADH in the process. It consists of several steps, and we need to identify if any of these steps involve the removal of water.

2. **Analyzing the Options**:
- **Fructose 6-phosphate to Fructose 1,6-bisphosphate**: This reaction is catalyzed by phosphofructokinase and involves the addition of a phosphate group from ATP. No water is removed.
- **Glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate**: This reaction involves the addition of a phosphate group and does not involve the removal of water.
- **2-phosphoglycerate to Phosphoenolpyruvate (PEP)**: This reaction is catalyzed by the enzyme enolase and involves the removal of a water molecule, making it a dehydration reaction.
- **Phosphoenolpyruvate to Pyruvic acid**: This reaction generates ATP but does not involve the removal of water.

3. **Identifying the Correct Reaction**: From the analysis, the reaction that involves the removal of a water molecule is the conversion of 2-phosphoglycerate to phosphoenolpyruvate (PEP).

4. **Conclusion**: Therefore, the correct answer to the question is that a molecule of water is removed during the conversion of 2-phosphoglycerate to phosphoenolpyruvate.

### Final Answer:
The reaction in glycolysis where a molecule of water is removed from the substrate is:
**2-phosphoglycerate to phosphoenolpyruvate (PEP)**.