The name for this large group of molecules comes from the early idea that they were made up of carbon and water. They are indeed made up of carbon, hydrogen, and oxygen atoms, though the oxygen and hydrogen are not found as intact water complexes within the molecules. Carbohydrates are produced by all plants and animals for the purpose of storing chemical energy, and by plants to make a supporting skeleton for its cells. Simple sugars and starch are energy stores, while pectins, cellulose, and other cell-wall carbohydrates are the plant’s structural materials.