The process in photosynthesis that utilizes energy from the sun is called the light-dependent reactions. These reactions occur in the thylakoid membranes of chloroplasts and involve the absorption of sunlight by chlorophyll and other pigments.
During the light-dependent reactions, sunlight is converted into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). Water molecules are also split (a process known as photolysis), producing oxygen as a byproduct. The energy captured from sunlight is essential for driving the subsequent stage of photosynthesis known as the Calvin cycle, where carbon dioxide is fixed and converted into glucose using the ATP and NADPH generated in the light-dependent reactions.