1st step (reaction) of glycolysis is -

Options

A. Oxidative step
B. Reductive step
C. Endergonic
D. Exergonic

Answer

### Step-by-Step Solution for the First Step of Glycolysis:

1. **Understanding Glycolysis**: Glycolysis is the metabolic pathway that breaks down glucose (a 6-carbon carbohydrate) into two molecules of pyruvate (a 3-carbon compound). This process occurs in the cytoplasm of the cell and is essential for both aerobic and anaerobic respiration.

2. **First Step of Glycolysis**: The first step of glycolysis involves the conversion of glucose into glucose-6-phosphate (G6P).

3. **Involvement of ATP**: In this step, glucose is phosphorylated by the addition of a phosphate group. This is facilitated by the enzyme hexokinase. The phosphate group is derived from ATP (adenosine triphosphate), which donates a phosphate group and is converted into ADP (adenosine diphosphate) in the process.

4. **Energy Release**: The conversion of ATP to ADP releases energy, which is utilized to add the phosphate group to glucose. This process is known as an exergonic reaction, where energy is released.

5. **Result of the Reaction**: The final product of this first step is glucose-6-phosphate (G6P), which is now ready to undergo further transformations in the glycolytic pathway.

### Summary of the First Step:
- **Input**: Glucose + ATP
- **Output**: Glucose-6-phosphate (G6P) + ADP + Energy