During glycolysis, phosphorylation of glucose is catalysed by :

Options

A. hexokinase
B. phosphorylase
C. phosphoglucoisomerase
D. phosphoglucomutase

Explanation

**Step-by-Step Text Solution:**

1. **Understanding Phosphorylation**: Phosphorylation is the process of adding a phosphoryl group (PO4) to a molecule. In the context of glycolysis, this refers to the addition of a phosphate group to glucose.

2. **Role of Phosphorylation in Glycolysis**: The phosphorylation of glucose is a crucial step in glycolysis. When glucose enters the cell, it can potentially leave again. To prevent this, glucose is phosphorylated to form glucose 6-phosphate, which is charged and cannot easily cross the cell membrane.

3. **Enzyme Involved**: The enzyme that catalyzes the phosphorylation of glucose during glycolysis is **hexokinase**. Hexokinase uses ATP to add a phosphate group to glucose, converting it into glucose 6-phosphate.

4. **Elimination of Other Options**:
- **Phosphorylase**: This enzyme is involved in glycogenolysis, the breakdown of glycogen, not in the phosphorylation of glucose.
- **Phosphoglucoisomerase**: This enzyme converts glucose 6-phosphate into fructose 6-phosphate, but it does not catalyze the phosphorylation of glucose.
- **Phosphoglucomutase**: This enzyme is involved in the conversion of 3-phosphoglycerate into 2-phosphoglycerate and is not related to the phosphorylation of glucose.

5. **Conclusion**: Therefore, the enzyme that catalyzes the phosphorylation of glucose during glycolysis is **hexokinase**.

---