ATP formation in glycolysis is

Options

A. Oxidative phosphorylation
B. Photophosphorylation
C. Reductive phosphorylation
D. Substrate level phosphorylation

Explanation

**Step-by-Step Solution:**

1. **Understanding Glycolysis**: Glycolysis is the metabolic pathway that converts glucose into pyruvate, producing energy in the form of ATP. It occurs in the cytoplasm of the cell and is the first step in cellular respiration.

2. **ATP Formation in Glycolysis**: During glycolysis, ATP is generated through a process known as substrate-level phosphorylation. This is a direct method of synthesizing ATP from ADP and inorganic phosphate using energy released from the breakdown of glucose.

3. **Types of Phosphorylation**:
- **Oxidative Phosphorylation**: This occurs in the mitochondria and involves the electron transport chain, where ATP is produced indirectly through the transfer of electrons and the establishment of a proton gradient.
- **Photophosphorylation**: This occurs in plants during photosynthesis and involves the conversion of light energy into chemical energy, leading to ATP formation.
- **Reductive Phosphorylation**: This is less common and involves the reduction of a molecule, typically associated with the addition of electrons.
- **Substrate-Level Phosphorylation**: This is the direct transfer of a phosphate group to ADP from a phosphorylated intermediate, which is the mechanism used during glycolysis.

4. **Conclusion**: In glycolysis, ATP is formed specifically through substrate-level phosphorylation. Therefore, the correct answer to the question is substrate-level phosphorylation.

**Final Answer**: The ATP formation in glycolysis is through substrate-level phosphorylation.

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