Which organelle is primarily responsible for photosynthesis in plant cells?

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Photosynthesis uses light energy to convert carbon dioxide and water into glucose, and in plant cells this process happens mainly inside chloroplasts. These organelles contain chlorophyll, the green pigment that captures light, and organize the light-dependent reactions in internal membranes called thylakoids. During these reactions, light energy is transformed into chemical energy as ATP and NADPH are produced, with oxygen released as a byproduct. The ATP and NADPH power the Calvin cycle in the surrounding stroma, where carbon dioxide is fixed into sugar. This combination of light capture and carbon fixation happens in chloroplasts, making them the primary site of photosynthesis.

Mitochondria generate ATP through cellular respiration rather than capturing light energy. The nucleus stores genetic information and directs cellular activities, while ribosomes synthesize proteins. So chloroplasts are the organelles that drive the photosynthetic process.