Where is ATP synthesized in glycolysis?

Options

A. When 1, 3 di PGA is changed into 3 PGA
B. When PEP is changed into pyruvic acid
C. When Fr. 1, 6 di P is broken in Triose phosphate (2 molecules)
D. Both a and b

Answer

### Step-by-Step Solution:

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

2. **Identifying ATP Synthesis**: In glycolysis, ATP is synthesized through a process known as substrate-level phosphorylation. This occurs at two key steps in the glycolytic pathway.

3. **First ATP Synthesis Step**:
- The first step where ATP is synthesized is during the conversion of 1,3-bisphosphoglycerate (1,3-BPG) to 3-phosphoglycerate (3-PGA).
- This reaction is catalyzed by the enzyme **phosphoglycerate kinase**.
- In this reaction, a phosphate group is transferred from 1,3-BPG to ADP, forming ATP.

4. **Second ATP Synthesis Step**:
- The second step occurs when phosphoenolpyruvate (PEP) is converted into pyruvate.
- This reaction is catalyzed by the enzyme **pyruvate kinase**.
- Here, another phosphate group is transferred from PEP to ADP, resulting in the formation of ATP.

5. **Conclusion**: Therefore, ATP is synthesized in glycolysis at two specific points:
- When 1,3-BPG is converted to 3-PGA (via phosphoglycerate kinase).
- When PEP is converted to pyruvate (via pyruvate kinase).

### Summary:
ATP is synthesized in glycolysis at two locations: during the conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate and during the conversion of phosphoenolpyruvate to pyruvate.

---