Substrate-level phosphoryalation accounts for approximately what percantage of the ATP formed by the reactions of glycolysis?

Options

A. `0%`
B. `2%`
C. `10%`
D. `100%`

Answer

**Step-by-Step Solution:**

1. **Understanding Glycolysis**: Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, producing ATP in the process. It consists of 10 enzymatic reactions.

2. **ATP Production in Glycolysis**: During glycolysis, a total of 8 ATP molecules are produced. This production occurs through two main processes: substrate-level phosphorylation and oxidative phosphorylation. However, in the context of glycolysis, we focus on substrate-level phosphorylation.

3. **Substrate-Level Phosphorylation**: This is a direct method of generating ATP. In this process, a phosphate group is directly transferred from a substrate to ADP, forming ATP.

4. **Identifying Substrates**: In glycolysis, two key substrates involved in substrate-level phosphorylation are:
- 1,3-diphosphoglyceric acid, which contributes to the formation of 6 ATP.
- Another substrate that contributes to the formation of 2 ATP.

5. **Calculating the Percentage**: Since all 8 ATP molecules produced in glycolysis are formed through substrate-level phosphorylation, we can conclude that:
- Total ATP produced = 8
- ATP produced by substrate-level phosphorylation = 8
- Therefore, the percentage of ATP formed by substrate-level phosphorylation = (8/8) * 100% = 100%.

6. **Final Answer**: Substrate-level phosphorylation accounts for approximately 100% of the ATP formed by the reactions of glycolysis.

---