Chemical compound composed of carbon, hydrogen, and oxygen, with the basic formula Cm(H2O)n, and related compounds with the same basic structure but modified functional groups. As sugar and starch, carbohydrates form a major energy-providing part of the human diet.
The simplest carbohydrates are sugars (monosaccharides, such as glucose and fructose, and disaccharides, such as sucrose), which are soluble compounds, some with a sweet taste. When these basic sugar units are joined together in long chains or branching structures they form polysaccharides, such as starch and glycogen, which often serve as food stores in living organisms. Even more complex carbohydrates are known, including chitin, which is found in the cell walls of fungi and the hard outer skeletons of insects, and cellulose, which makes up the cell walls of plants. Carbohydrates form the chief foodstuffs of herbivorous animals.
An essential structural component of living cells and source of energy for animals; includes simple sugars with small molecules as well as macromolecular substances; classified according to their number of monosaccharide groups.