"Carbohydrate"

A carbohydrate (/ˌkɑːrboʊˈhaɪdreɪt/) are sugars (saccharaides) and their derivatives. For the simplest carbohydrates, the carbon-to-hydrogen-to-oxygen atomic ratio is 1:2:1, i.e. they are represented by the empirical formula C(H₂O)_n. Many variants on this idealized formula exist. Conversely, some compounds conforming to this definition, such as formaldehyde are not classified as carbohydrates. Together with amino acids, fats, and nucleic acids, the carbohydrates are one of the major families of biomolecules.

The term is predominantly used in biochemistry, functioning as a synonym for saccharide (from Ancient Greek σάκχαρον (sákkharon) 'sugar'), a group that includes sugars, starch, and cellulose. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest (lower molecular weight) carbohydrates, are commonly referred to as sugars. While the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose, which was originally taken from the word glucose (from Ancient Greek γλεῦκος (gleûkos) 'wine, must'), and is used for almost all sugars (e.g., fructose (fruit sugar), sucrose (cane or beet sugar), ribose, lactose (milk sugar)).

Carbohydrates perform numerous roles in living organisms. Polysaccharides serve as an energy store (e.g., starch and glycogen) and as structural components (e.g., cellulose in plants and chitin in arthropods and fungi). The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g., ATP, FAD and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.

Carbohydrates are central to nutrition and are found in a wide variety of natural and processed foods. Starch is a polysaccharide and is abundant in cereals (wheat, maize, rice), potatoes, and processed food based on cereal flour, such as bread, pizza or pasta. Sugars appear in human diet mainly as table sugar (sucrose, extracted from sugarcane or sugar beets), lactose (abundant in milk), glucose and fructose, both of which occur naturally in honey, many fruits, and some vegetables. Table sugar, milk, or honey is often added to drinks and many prepared foods such as jam, biscuits and cakes.

Cellulose, a polysaccharide found in the cell walls of all plants.