Final answer:
The light reactions of photosynthesis start with the absorption of sunlight by chlorophyll in the chloroplast. The major products of the light reactions are ATP and NADPH, which are used in the Calvin cycle to synthesize carbohydrates. Oxygen is also released as a by-product of the light reactions.
Step-by-step explanation:
The light reactions of photosynthesis start with the absorption of sunlight by the pigment chlorophyll in the thylakoid membranes of the chloroplast. The energy from sunlight is then transferred to ATP and NADPH, which are the major products of the light reactions. In addition to ATP and NADPH, oxygen is also produced as a by-product of the light reactions.
ATP and NADPH are used in the second stage of photosynthesis, called the light-independent reactions or Calvin cycle, to synthesize carbohydrates from carbon dioxide.