carbohydrate

carbohydrate any member of a large class of chemical compounds that includes sugars, starches, cellulose, and related compounds. These compounds are produced naturally by green plants from carbon dioxide and water (see photosynthesis ). Carbohydrates are important as foods; they supply energy and are used in the production of fats. They are also used in various forms in industry and commerce. There are three main classes of carbohydrates. Monosaccharides are the simple sugars, e.g., fructose and glucose ; they have the general formula (CH ₂ O) _n , in which n is an integer larger than 2. Disaccharides include lactose , maltose , and sucrose . Upon hydrolysis, a disaccharide molecule yields two monosaccharide molecules. Most disaccharides have the general formula C _n (H ₂ O) _n-1 , with n larger than 5. Polysaccharides include such substances as cellulose , dextrin , glycogen , and starch ; they are polymeric compounds made up of the simple sugars and can be hydrolyzed to yield simple sugars. The disaccharides are sometimes grouped with the simpler polysaccharides (usually those made up of three or four simple sugar units) to form a class of carbohydrates called the oligosaccharides.

carbohydrate Organic compound of carbon, hydrogen and oxygen that is a constituent of many foodstuffs. The simplest carbohydrates are sugars. Glucose and fructose are monosaccharides, naturally occurring sugars; they have the same formula (C₆H₁₂O₆) but different structures. One molecule of each combines with the loss of water to make sucrose (C₁₂H₂₂O₁₁), a disaccharide. Starch and cellulose are polysaccharides, carbohydrates consisting of hundreds of glucose molecules linked together. The popular Atkins diet is based on not eating foods with carbohydrates, such as bread and potatoes. See also saccharide

carbohydrate One of a group of organic compounds based on the general formula C_x(H₂O)_y. The simplest carbohydrates are the sugars (saccharides), including glucose and sucrose. Polysaccharides are carbohydrates of much greater molecular weight and complexity; examples are starch, glycogen, and cellulose. Carbohydrates perform many vital roles in living organisms. Sugars, notably glucose, and their derivatives are essential intermediates in the conversion of food to energy. Starch and other polysaccharides serve as energy stores in plants, particularly in seeds, tubers, etc., which provide a major energy source for animals, including humans. Cellulose, lignin, and others form the supporting cell walls and woody tissue of plants. Chitin is a structural polysaccharide found in the body shells of many invertebrate animals. Carbohydrates also occur in the surface coat of animal cells and in bacterial cell walls.