Animation showing the photoexcitation of an electron at the start of photosynthesis in a plant. Photosynthesis is the process by which plants convert sunlight and carbon dioxide into sugars. The initial step occurs when light (red wave) is absorbed by an atom, causing an electron (yellow) to be raised to a higher energy level. This excited electron is then passed to an acceptor molecule (grey). In green plants, the electron is first excited in a chlorophyll molecule, and passed to a molecule of pheophytin. The electron is then passed through a complicated chain of molecules to produce the energy to make sugars. See clip K003 7543 for an animation of the electron transport chain.