Substrate phosphorylation is the formation of

Options

A. ATP
B. AMP
C. ADP
D. Pyruvic acid

Answer

### Step-by-Step Solution:

1. **Understanding Substrate Phosphorylation**:
Substrate phosphorylation refers to the direct formation of ATP from ADP through the transfer of a phosphate group from a phosphorylated compound.

2. **Identifying the Options**:
The options given are ATP, AMP, ADP, and pyruvic acid. We need to determine which of these is formed through substrate-level phosphorylation.

3. **Eliminating Incorrect Options**:
- **Pyruvic Acid**: This is the end product of glycolysis and does not directly relate to substrate phosphorylation, so we can eliminate this option.
- **AMP and ADP**: These are nucleotides involved in energy transfer, but they are not the products of substrate-level phosphorylation.

4. **Focusing on ATP**:
The process of substrate-level phosphorylation specifically results in the formation of ATP. This occurs when a high-energy phosphate group is transferred to ADP, converting it into ATP.

5. **Example from Glycolysis**:
In glycolysis, substrate-level phosphorylation occurs in two steps. For example, during the conversion of 1,3-diphosphoglycerate to 3-phosphoglycerate, a phosphate group is transferred to ADP, forming ATP. This reaction is catalyzed by the enzyme phosphoglycerokinase.

6. **Conclusion**:
Based on the explanation and examples provided, the correct answer to the question is **ATP**.