In which organelle does the light-dependent reaction of photosynthesis occur?

• A. Chloroplast stroma
• B. Mitochondria
• C. Thylakoid membranes of chloroplasts
• D. Ribosomes

Answer: (C)

The light-dependent reactions of photosynthesis take place in the thylakoid membranes of chloroplasts. During these reactions, chlorophyll and other pigments located in the thylakoid membranes absorb light energy, which is then used to convert water molecules into oxygen gas and produce energy carriers such as ATP and NADPH.

The organization of thylakoids into stacks called granum increases the surface area for light absorption, allowing for more efficient energy capture. The light-dependent reactions are essential as they provide the energy and reducing power necessary for the subsequent light-independent reactions, commonly known as the Calvin cycle, which occur in the chloroplast stroma.