The main purpose of the light-dependent reactions is to convert light energy from the sun into chemical energy in the form of ATP and NADPH. These energy carriers are then used by the Calvin cycle (the light-independent reactions) to synthesize sugars and other organic compounds. Key points

• Location: Occur in the thylakoid membranes of chloroplasts in plants, algae, and cyanobacteria.
• Primary outputs: ATP and NADPH, produced as electrons are excited by light and transferred through photosystems and electron transport chains.
• Role in photosynthesis: The ATP and NADPH generated provide the energy and reducing power required to drive the carbon fixation and sugar synthesis steps of the Calvin cycle.