Photosynthesis occurs in two stages: the light-dependent stage and light-independent (dark) stage. In the dark reaction, also known as the Calvin cycle, the protons and electrons are used to reduce Carbon Dioxide (CO₂) and water (H₂O) to carbohydrate (CH₂O). This reaction uses ATP and NADPH to convert CO₂ and H₂O into CH₂O, regenerating ADP and NADP⁺. The reaction took place in the chloroplast stroma, outside the thylakoids.
