Photosynthesis occurs in the chloroplasts of plant cells and consists of two stages: Light-dependent reactions: These take place in the thylakoid membranes and use light energy to produce ATP and NADPH while releasing oxygen. Calvin Cycle: This occurs in the stroma of the chloroplasts and uses ATP and NADPH to convert carbon dioxide into glucose. Chloroplasts contain chlorophyll, the pigment that absorbs light energy necessary for photosynthesis.