- Mainly sugars and starches, together constituting one of the three principal types of nutrients used as energy sources (calories) by the body. Carbohydrates can also be defined chemically as neutral compounds of carbon, hydrogen and oxygen. Carbohydrates come in simple forms such as sugars and in complex forms such as starches and fiber. The body breaks down most sugars and starches into glucose, a simple sugar that the body can use to feed its cells. Complex carbohydrates are derived from plants. Dietary intake of complex carbohydrates can lower blood cholesterol when they are substituted for saturated fat. Carbohydrates are classified into mono, di, tri, poly and heterosaccharides. The smallest carbohydrates are monosaccharides such as glucose whereas polysaccharides such as starch, cellulose and glycogen can be large and even indeterminate in length. The energy produced by carbohydrates is 4 calories per gram. Proteins also provide 4 calories per gram. Fats are high-cal; they provide 9 calories per gram. Etymology: Carbohydrates are called carbohydrates because the carbon, hydrogen and oxygen they contain are usually in the proportion to form water with the general formula Cn(H2O)n.
* * *Class name for the aldehydic or ketonic derivatives of polyhydric alcohols, the name being derived from the fact that the most common examples of such compounds have formulas that may be written as Cn(H2O)n ( e.g., glucose, C6(H2O)6; sucrose, C12(H2O)11), although they are not true hydrates and the name is, in that sense, a misnomer. The group includes compounds with relatively small molecules, such as the simple sugars (monosaccharides, disaccharides, etc.), as well as macromolecular (polymeric) substances such as starch, glycogen, and cellulose. The c. most typical of the class contain carbon, hydrogen, and oxygen only, but carbohydrate metabolic intermediates in tissues also contain phosphorus. See saccharides.
Medical dictionary. 2011.