Which organelle is primarily responsible for photosynthesis in plant cells?

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

Answer: (D)

Photosynthesis is the process plants use to turn light energy into chemical energy stored as glucose, and it happens in chloroplasts. These organelles contain chlorophyll, the light-absorbing pigment, and their internal structures (thylakoid membranes and the surrounding stroma) carry out the two main stages: light-dependent reactions that capture light to make ATP and NADPH, and the Calvin cycle that uses those energy carriers to fix carbon dioxide into sugars. Mitochondria, by contrast, release energy from glucose to power the cell; the nucleus stores genetic material and regulates activity; lysosomes break down waste. Because chloroplasts are specialized for harvesting light and driving the chemical synthesis of sugars, they are the primary site of photosynthesis in plant cells.