During glycolysis , isomerization occurs in how many steps ?

Options

A. 2
B. 3
C. 4
D. 5

Answer

To determine how many steps of isomerization occur during glycolysis, we can analyze the glycolytic pathway step by step.

### Step-by-Step Solution:

1. **Understanding Glycolysis**: Glycolysis is the metabolic pathway that converts glucose into pyruvate, producing ATP and NADH in the process. It consists of several enzymatic reactions.

2. **Identifying Isomerization Steps**:
- **First Isomerization**: The first isomerization occurs when glucose-6-phosphate is converted to fructose-6-phosphate. This reaction is catalyzed by the enzyme phosphohexose isomerase.
- **Second Isomerization**: The second isomerization occurs when dihydroxyacetone phosphate (DHAP) is converted to glyceraldehyde-3-phosphate (G3P). This is an interconversion between two forms of a triose sugar, catalyzed by the enzyme triose phosphate isomerase.
- **Third Isomerization**: The third isomerization occurs when 3-phosphoglycerate is converted to 2-phosphoglycerate. This reaction is catalyzed by the enzyme phosphoglycerate mutase.

3. **Counting the Isomerization Steps**:
- From the analysis, we can see that there are three distinct isomerization steps in glycolysis:
1. Glucose-6-phosphate to Fructose-6-phosphate
2. Dihydroxyacetone phosphate to Glyceraldehyde-3-phosphate
3. 3-Phosphoglycerate to 2-Phosphoglycerate

4. **Conclusion**: Therefore, the total number of isomerization steps that occur during glycolysis is **3**.

### Final Answer:
The answer is **3**.

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