Which of the given enzymes of glycolysis is required at the beginning of process ?

Options

A. Hexokinase
B. Aldolase
C. Isomerase
D. Mutase

Answer

### Step-by-Step Solution:

1. **Understanding Glycolysis**: Glycolysis is the first step of cellular respiration, occurring in both aerobic and anaerobic conditions. It consists of two main phases: the preparatory phase and the payoff phase.

2. **Identifying the Phases**:
- The **preparatory phase** involves the investment of energy and includes the first five reactions.
- The **payoff phase** involves the release of energy and includes the last five reactions.

3. **Analyzing the Enzymes**: The question asks which enzyme is required at the beginning of glycolysis. The options provided are:
- Hexokinase
- Aldolase
- Isomerase
- Mutase

4. **Determining the First Enzyme**:
- **Hexokinase**: This is the first enzyme in glycolysis that catalyzes the conversion of glucose to glucose-6-phosphate by adding a phosphate group. This step is crucial as it marks the beginning of the glycolytic pathway.
- **Aldolase**: This enzyme catalyzes the conversion of fructose-1,6-bisphosphate into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, but it is not the first enzyme.
- **Isomerase**: This enzyme converts glyceraldehyde-3-phosphate into dihydroxyacetone phosphate, also not the first enzyme.
- **Mutase**: This enzyme is involved in the payoff phase and converts 3-phosphoglycerate to 2-phosphoglycerate, making it irrelevant to the initial steps of glycolysis.

5. **Conclusion**: The enzyme required at the beginning of glycolysis is **Hexokinase**, as it is the first enzyme that initiates the glycolytic process by phosphorylating glucose.

### Final Answer:
The enzyme required at the beginning of glycolysis is **Hexokinase**.

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