plants use their leaves to intercept sunlight. the energy is used to reduce carbon dioxide from the air with electrons from water to make sugars (and other biomass) and a waste product, oxygen, in the process of photosynthesis. leaves also respire, in a similar way to animals, by burning their biomass to generate chemical energy. this energy is temporarily stored in the form of atp (adenosine triphosphate), which acts as an energy currency for metabolism in all living things. as a waste product, respiration produces carbon dioxide.