Other organisms depend on glucose produced by photosynthesis for energy to fuel biological processes such as cellular respiration. During cellular respiration, organisms split glucose back into water and carbon dioxide. The breaking down of glucose releases and utilizes energy from the sun stored by photosynthesizing plants. The oxygen level of the Earth's atmosphere is largely reliant on the amount of photosynthetic activity and respiration going on in the biosphere. A build up of elements in areas with a lot of organisms is prevented by circulation of the atmosphere with global air currents.