- 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.
* * *car·bo·hy·drate -.drāt, -drət n any of various neutral compounds of carbon, hydrogen, and oxygen (as sugars, starches, and celluloses) most of which are formed by green plants and which constitute a major class of animal foods
* * *n.any one of a large group of compounds, including the sugar and starch, that contain carbon, hydrogen, and oxygen and have the general formula Cx(H2O)y. Carbohydrates are important as a source of energy: they are manufactured by plants and obtained by animals from the diet, being one of the three main constituents of food (see also fat, protein). All carbohydrates are eventually broken down in the body to the simple sugar glucose, which can then take part in energy-producing metabolic processes. Excess carbohydrate, not immediately required by the body, is stored in the liver and muscles in the form of glycogen. In plants carbohydrates are important structural materials (e.g. cellulose) and storage products (commonly in the form of starch). See also disaccharide, monosaccharide, polysaccharide.
* * *car·bo·hy·drate (kahr″bo-hiґdrāt) any of a class of aldehyde or ketone derivatives of polyhydric alcohols, particularly of the pentahydric and hexahydric alcohols. They are so named because the hydrogen and oxygen are usually in the proportion to form water, Cn(H2O)n; the most important include the small sugars as well as the large starches, glycogens, celluloses, and gums. See also saccharide.
Medical dictionary. 2011.