Photosynthesis runs in two linked stages inside chloroplasts:

• Light-dependent reactions happen in the thylakoid membranes. Chlorophyll absorbs photons and uses their energy to split water, releasing O2 and making the energy carriers ATP and NADPH
• Light-independent reactions (the Calvin cycle) happen in the stroma. They use that ATP and NADPH to build glucose from CO2, one carbon at a time
• The Calvin cycle takes in one CO2 per turn, so it needs six turns to make one glucose molecule