Photosynthesis and cellular respiration essentially represent the cyclical flow of energy between plants and animals. Photosynthesis is the process by which plants take the energy from sunlight to convert carbon dioxide and water into glucose and oxygen. The glucose is used as a form of stored chemical energy and the oxygen is released to the atmosphere. The animals in turn use the oxygen (from breathing) and glucose (from eating) from plants to undergo cellular respiration. This process converts the glucose and oxygen back into carbon dioxide and water. The animals utilize this process to produce energy in the form of ATP, and the carbon dioxide and water are released back into the atmosphere for the plants to reuse and start the whole cycle over again.