Which one of the following is the first step glycolysis ?

Options

A. Breakdown of glucose
B. Phosphorylation of glucose
C. Conversion of glucose into fructose
D. Dehydrogenation of glucose

Answer

### Step-by-Step Text Solution:

1. **Understanding Glycolysis**: Glycolysis is a metabolic pathway that converts glucose into pyruvate, producing energy in the form of ATP and NADH in the process. It occurs in the cytoplasm of the cell.

2. **Identifying the First Step**: The first step of glycolysis involves the conversion of glucose into glucose 6-phosphate.

3. **Enzyme Involved**: This conversion is catalyzed by the enzyme hexokinase.

4. **Reaction Details**: During this reaction, one molecule of ATP is consumed, and one molecule of ADP is produced.

5. **Irreversibility of the Step**: This step is considered irreversible, which means that once glucose is phosphorylated to glucose 6-phosphate, it cannot revert back to glucose easily.

6. **Importance of Phosphorylation**: The addition of the phosphate group to glucose (forming glucose 6-phosphate) prevents glucose from passing through the plasma membrane, thus trapping it inside the cell for further processing in glycolysis.

7. **Conclusion**: Therefore, the first step of glycolysis is the phosphorylation of glucose to form glucose 6-phosphate.