Which of the following steps is associated with ATP formation (substrate level phosphorylation)?

Options

A. Succinly `CoA rarr` Succinic acid
B. 1,3 bis `PGA rarr 3PGA`
C. `PEP rarr` Pyruvate
D. All of these

Answer

To solve the question about which steps are associated with ATP formation through substrate-level phosphorylation, we can break down the options provided:

### Step-by-Step Solution:

1. **Understanding Substrate-Level Phosphorylation**:
- Substrate-level phosphorylation is a process where ATP is formed by the direct transfer of a phosphate group from a phosphorylated substrate to ADP, resulting in ATP. This occurs during specific enzymatic reactions.

2. **Analyzing Each Option**:
- **Option 1: Succinyl Coenzyme A to Succinic Acid**:
- This reaction occurs in the Krebs cycle and is catalyzed by the enzyme succinyl coenzyme A synthetase. During this reaction, GTP is formed, which can be converted to ATP. This is a substrate-level phosphorylation event.

- **Option 2: 1,3-Bisphosphoglycerate to 3-Phosphoglycerate**:
- This reaction is part of glycolysis and is catalyzed by the enzyme phosphoglycerate kinase. In this reaction, ATP is formed from ADP and inorganic phosphate, indicating substrate-level phosphorylation.

- **Option 3: Phosphoenolpyruvate (PEP) to Pyruvate**:
- This reaction also occurs during glycolysis and is catalyzed by the enzyme pyruvate kinase. Here, ATP is produced from ADP and inorganic phosphate, which is another example of substrate-level phosphorylation.

3. **Conclusion**:
- Since all three reactions (1, 2, and 3) involve the formation of ATP through substrate-level phosphorylation, the correct answer to the question is **Option 4: All of these**.

### Final Answer:
**All of these (Option 4)** are associated with ATP formation through substrate-level phosphorylation.

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