The energy required to drive nutrient cycling is obtained by processes occurring in the biosphere. The primary source of energy for ecosystem processes is photosynthesis. Directly or indirectly, photosynthesis provides the energy for all forms of life in the biosphere. Photosynthesis utilizes energy from the sun to reduce CO2<span> into high energy organic compounds. Subsequently, the energy contained in these organic compounds is released by the process of respiration. The respiration process releases energy by oxidizing the high energy bonds of the organic compounds, the energy released being used to perform all the metabolic processes of biota.
Enzymes lower the activation energy, making life possible to occur as the reactions can happen quickly. But, they can be affected by temperature or pH, and they are always being constantly reused over and over in reactions.
