Chloroplasts absorb energy from sunlight. The green pigment chlorophyll within the chloroplast captures light energy from the sun, which is then used to power the process of photosynthesis, converting carbon dioxide and water into glucose and oxygen. This process occurs in two main stages: the light reactions, where sunlight excites electrons and generates ATP and NADPH, and the carbon-fixation reactions (Calvin cycle), which use that energy to produce carbohydrates. The energy absorbed by chlorophyll specifically excites electrons that drive this entire photosynthetic process.
