How many ATP molecules are directly synthesised in glycolysis?

Options

A. 6ATP
B. 4ATP
C. 36ATP
D. 8ATP

Answer

To determine how many ATP molecules are directly synthesized in glycolysis, we can follow these steps:

### Step-by-Step Solution:

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

2. **ATP Production in Glycolysis**: During glycolysis, ATP is produced through substrate-level phosphorylation. This process occurs in two phases: the energy investment phase and the energy payoff phase.

3. **Energy Investment Phase**: In the first half of glycolysis, 2 ATP molecules are consumed to phosphorylate glucose and its intermediates. This is necessary for the subsequent steps.

4. **Energy Payoff Phase**: In the second half of glycolysis, 4 ATP molecules are produced. This occurs as the three-carbon molecules (glyceraldehyde-3-phosphate) are converted into pyruvate.

5. **Net Gain of ATP**: Although 4 ATP molecules are produced in total during glycolysis, since 2 ATP molecules were used in the energy investment phase, the net gain of ATP from glycolysis is 2 ATP molecules.

6. **Final Answer**: Therefore, the question asks for the number of ATP molecules directly synthesized in glycolysis. The correct answer is that 4 ATP molecules are produced, but the net gain is 2 ATP.

### Conclusion:
The correct answer to the question is that 4 ATP molecules are directly synthesized in glycolysis, but the net gain is 2 ATP.

---