Which cellular component is the site of photosynthesis?

• A. Nucleus
• B. Cytoplasm
• C. Mitochondria
• D. Chloroplasts

Answer: (D)

Photosynthesis happens inside chloroplasts, the green organelles in plant and algal cells that contain chlorophyll. These pigments capture light energy and drive the chemical steps that convert carbon dioxide and water into glucose. Within chloroplasts, the light-dependent reactions occur on the thylakoid membranes, using light to generate ATP and NADPH, while the Calvin cycle runs in the stroma to fix CO2 into sugars. The nucleus houses genetic material, the cytoplasm is the fluid where many cellular processes take place, and mitochondria are the powerhouses of cellular respiration, not photosynthesis. Because the key machinery and pigments for capturing light and driving sugar formation reside in chloroplasts, they are the site where photosynthesis occurs.