AIMS Science Practice Test

Light energy powers photosynthesis in chloroplasts. Pigments like chlorophyll absorb sunlight and use that energy to drive the reactions that make chemical energy in the form of ATP and NADPH. Those molecules then fuel the Calvin cycle, where carbon dioxide is fixed into sugars, ultimately forming glucose. So the initial energy input is light energy, not motion or stored chemical energy. Chemical energy from ATP is produced during the process and used to build glucose, but it’s the light that starts everything.