ATP is formed by photosynthesizing plant cell by :

Options

A. Photophosphorylation
B. Oxidative Phosphorylation
C. Substrate level phosphorylation
D. All of the above

Explanation

To solve the question regarding how ATP is formed by photosynthesizing plant cells, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Understanding Photosynthesis**:
- Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water.
- During this process, ATP (adenosine triphosphate) is generated, which serves as an energy currency for the cell.

2. **Identifying the Processes**:
- The question presents several processes: photophosphorylation, oxidative phosphorylation, substrate-level phosphorylation, and all of the above.
- We need to determine which of these processes is primarily responsible for ATP formation in photosynthesizing plant cells.

3. **Photophosphorylation**:
- Photophosphorylation specifically refers to the synthesis of ATP using light energy.
- In photosynthesis, light energy is captured by chlorophyll and used to convert ADP (adenosine diphosphate) and inorganic phosphate into ATP.
- This process occurs in the thylakoid membranes of chloroplasts during the light-dependent reactions of photosynthesis.

4. **Oxidative Phosphorylation**:
- Oxidative phosphorylation occurs in cellular respiration, not photosynthesis.
- It involves the transfer of electrons through a series of proteins in the electron transport chain, leading to ATP production.
- Since this process is not related to photosynthesis, it is not the correct answer.

5. **Substrate-Level Phosphorylation**:
- Substrate-level phosphorylation occurs during glycolysis and the Krebs cycle, where a phosphate group is directly transferred to ADP to form ATP.
- This process does not primarily occur in the chloroplasts during photosynthesis, making it an incorrect choice for this question.

6. **Conclusion**:
- The only process directly associated with ATP formation during photosynthesis is photophosphorylation.
- Therefore, the correct answer to the question is **photophosphorylation**.

### Final Answer:
ATP is formed by photosynthesizing plant cells by **photophosphorylation**.