The Calvin cycle occurs in the stroma of the chloroplasts (Option C). This is the part of the chloroplast where the enzymes required for converting carbon dioxide into glucose are located.
To explain further, the stroma is a fluid-filled space inside the chloroplast surrounding the thylakoid membranes. It contains the necessary components for the Calvin cycle, including ribulose bisphosphate (RuBP), ATP, and NADPH produced in the light-dependent reactions of photosynthesis. The Calvin cycle uses these components to fix carbon dioxide into organic molecules, ultimately leading to the production of glucose.
Options A, B, and D are incorrect because:
- A. Chloroplast: While the stroma is a part of the chloroplast, the Calvin cycle specifically occurs in the stroma, not the entire chloroplast.
- B. Cytoplasm: The cytoplasm is where many other cellular processes occur, but the Calvin cycle does not take place there.
- C. Cell Wall: The cell wall provides structural support and protection for the cell but does not participate in the metabolic processes like the Calvin cycle.
In summary, the correct answer is C, the stroma, where the Calvin cycle takes place to synthesize sugars during photosynthesis.