Which organelle carries out photosynthesis in plants?

• A. Mitochondria
• B. Vacuole
• C. Chloroplasts
• D. Ribosome

Answer: (C)

Light energy is captured and used to build sugars in chloroplasts, the plant cell organelles where photosynthesis happens. Inside chloroplasts, the light-dependent reactions take place in the thylakoid membranes, using light to split water and release oxygen while producing ATP and NADPH. Those energy carriers feed the Calvin cycle in the surrounding fluid (the stroma), where carbon dioxide is fixed into sugars. Chloroplasts also contain chlorophyll, the pigment that absorbs light to drive the process. The other organelles don’t perform photosynthesis: mitochondria generate energy through respiration, vacuoles mainly store water and other substances, and ribosomes synthesize proteins.