(redirected from Complex carbohydrates)
Also found in: Dictionary, Thesaurus, Medical.


see carbohydratecarbohydrate,
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).
..... Click the link for more information.
The Columbia Electronic Encyclopedia™ Copyright © 2013, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/


A class of high-molecular-weight carbohydrates, colloidal complexes, which break down on hydrolysis to monosaccharides containing five or six carbon atoms. The polysaccharides are considered to be polymers in which monosaccharides have been glycosidically joined with the elimination of water. A polysaccharide consisting of hexose mono-saccharide units may be represented by the reaction below.

The term polysaccharide is limited to those polymers which contain 10 or more monosaccharide residues. Polysaccharides such as starch, glycogen, and dextran consist of several thousand d -glucose units. Polymers of relatively low molecular weight, consisting of two to nine monosaccharide residues, are referred to as oligosaccharides. See Dextran, Glucose, Glycogen, Monosaccharide, Starch

Polysaccharides are often classified on the basis of the number of monosaccharide types present in the molecule. Polysaccharides, such as cellulose or starch, that produce only one monosaccharide type ( d -glucose) on complete hydrolysis are termed homopolysaccharides. On the other hand, polysaccharides, such as hyaluronic acid, which produce on hydrolysis more than one monosaccharide type (N-acetylglucosamine and d -glucuronic acid) are named heteropolysaccharides. See Carbohydrate

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a macromolecular compound of the carbohydrate class, composed of monosaccharide residues (M) joined by glycoside bonds. The molecular weight of polysaccharides ranges from several thousand for laminarin and inulin to several million for hyaluronic acid and glycogen; it can be determined only approximately, since individual polysaccharides are usually mixtures of components that differ in degree of polymerization. The chemical classification of polysaccharides is based on the structure of their monosaccharide components, hexoses (glucose, galactose, and mannose) and pentoses (arabinose and xylose), as well as amino sugars (glucosamine and galactosa-mine), deoxy sugars (rhamnose and fucose), and uronic acids.

Acid residues (acetic, pyruvic, lactic, phosphoric, and sulfuric acids) or alcohol residues (usually methanol) may be attached to hyroxyl (—OH) and amino (—NH2) groups in the molecules of natural polysaccharides. Homopolysaccharides are formed from residues of only one monosaccharide (for example, glucans and fructans), whereas heteropolysaccharides are composed of residues of two or more monosaccharides (for example, arabinoga-lactans, glycuronoxylans). Many common polysaccharides or polysaccharide groups bear long-established names, such as cellulose, starch, chitin, and pectins. (The name of a polysaccharide sometimes is associated with its source of extraction—for example, nigeran from the fungus Aspergillus niger and odontalan from the seaweed Odontalia corymbifera.)

Polysaccharides, unlike other classes of biopolymers, can exist in both a linear structural form (Figure 1,a) and branched forms (Figure 1,b and c).

Figure 1

Examples of linear polysaccharides are cellulose, amylose, and mucopolysaccharides; yeast mannans and vegetable gums have structure (b), and glycogen, amylopectin, and galactan from the edible snail Helix pomatia have structure (c). The structural type of a polysaccharide largely determines its physicochemical properties, particularly solubility in water. Regular linear polysaccharides (that is, those containing only one type of inter-monosaccharide bond), such as cellulose and chitin, are insoluble in water, since the energy of molecular interaction is greater than the hydration energy. Highly branched polysaccharides that do not have an ordered structure are readily soluble in water. The chemical reactions characteristic of many monosaccharides—for example, acylation, alkylation, oxidation of hy-droxyl groups, reduction of carboxyl groups, and the introduction of new groups—are also effected in polysaccharides, although the rates of these reactions are usually lower. Chemically modified polysaccharides often exhibit new properties of practical importance that are absent in the original compound.

Most polysaccharides are resistant to alkalies; their depolym-erization, or hydrolysis, takes place under the action of acids to yield free monosaccharides or oligosaccharides, depending on the conditions of acid hydrolysis. Molecules of heteropolysaccharides containing glycoside bonds of differing acid resistance can be split selectively; specific enzymes are also used for this purpose. Determination of the structure of low-molecular weight decomposition products simplifies the task of establishing the structure of the polysaccharide itself, reducing it to determination of the structure of the repeating units; it is believed—and has been shown using several examples—that all polysaccharides are composed of such units. Research on the secondary polysaccharide structure is conducted using physicochemical methods, particularly X-ray structural analysis, which has been successfully used in studying cellulose.

The biological functions of polysaccharides are extremely diverse. Starch and glycogen are reserve polysaccharides in plants and animals, whereas plant cellulose and the chitin in insects and fungi are structural polysaccharides. Hyaluronic acid, which occurs in the ovicellular membrane, synovia, and the vitreous humor, is a highly effective “lubricant.” Gums and mucosa in plants and capsular polysaccharides in microorganisms fulfill protective functions; the highly sulfated polysaccharide heparin inhibits blood clotting. Polysaccharide components in mixed carbohydrate-containing biopolymers such as glycoproteins and lipopolysaccharides, which are present in the surface cell layer, govern the specific immune reactions of the organism. Extracellular polysaccharides and other carbohydrate-containing biopolymers ensure intercellular reactions and the fixing of cells in plants (pectins) and animals (hyalin).

Polysaccharide biosynthesis is mainly effected with the participation of nucleoside diphosphate sugars, which act as donors of the monosaccharide or, less frequently, disaccharide residues that are transferred onto the corresponding oligosaccharide fragments of the polysaccharide being formed. The biosynthesis of heteropolysaccharides is effected by the successive addition of monosaccharides from the corresponding nucleoside diphosphate sugars to the polysaccharide chain. Another mechanism is also observed during the formation of polysaccharides in bacterial antigens: first the specific repeating units are synthesized, with the participation of lipid and nucleotide carriers of sugars; polysaccharides are then synthesized from the units under the action of the enzyme polymerase. Branched polysaccharides of the glycogen and amylopectin type are formed by the intramolecular enzymatic rearrangement of a linear polysaccharide. Approaches to the directed chemical synthesis of polysaccharides are being developed.

In living organisms, polysaccharides—which are the main energy reserves—are split by intracellular and extracellular enzymes to yield monosaccharides and their derivatives, which decompose further to liberate energy. The accumulation and decomposition of glycogen in the liver of humans and higher animals is a means of controlling the glycogen level in the blood. Monomeric products are formed indirectly by the successive splitting off of polysaccharides from the molecule or as a result of the step-by-step decomposition of polysaccharides, with the intermediate formation of oligosaccharides. Many polysaccharides, including starch, cellulose, and pectins, are used in the food and chemical industries, as well as in medicine.


Stacey, M., and S. Barker. Uglevody zhivykh tkanei. Moscow, 1965. (Translated from English.)
Khimiia uglevodov. Moscow, 1967.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A carbohydrate composed of many monosaccharides. Also known as glycan.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


, polysaccharose
any one of a class of carbohydrates whose molecules contain linked monosaccharide units: includes starch, inulin, and cellulose. General formula: (C6H10O5)n
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
The search for structure could help put to rest a long-running debate in the scientific community as to whether complex carbohydrate biopolymers require a defined structure to function.
Complex carbohydrates, such as multi-grain toast, porridge or granola, slowly release energy and give a prolonged boost to your blood sugar levels, preventing snacking and hunger.
Only Group B achieved the goal of reducing sugar intake, and only Group A achieved the goal of increasing complex carbohydrates.
Like genes and proteins, complex carbohydrates may be altered as cancer develops.
Ideally, you would eat complex carbohydrates, such as vegetables and whole grains that break down slowly, releasing glucose into your bloodstream over a period of time, and providing your body with a steady generation of energy rather than a burst.
Coverage includes the isolation, purification, and structural characterization of carbohydrates; the study of glycosylation in living cells; the exploitation of the "glycosylation machinery" for the production of complex carbohydrates in living cells; cell-free enzymatic methods for carbohydrate synthesis; chemical synthetic methods; industrial and biotechnological applications; applications in biomedicine and human health; and the types of carbohydrates--polysaccharides, oligosaccharides, and monosaccharides.
-ALTU fruit bars contain at least 20 per cent fruit, are full of complex carbohydrates (the ones that give you energy for longer) and lots of grains, rice and oats.
The GI rules include: Eat three meals a day, never skipping breakfast, and three snacks Eat lots of fruit and vegetables every day Drink plenty of water Eat 100 per cent stone-ground wholemeal bread and brown rice, complex carbohydrates which release their energy slowly Snacks These can include, an apple, orange, peach or pear; low fat sugar free yoghurt; 100g (4oz) low fat cottage cheese with one tablespoon sugar-free jam.
By replacing processed and additive-packed products with those rich in nutrients and complex carbohydrates - so-called 'happy foods', you will feel full of stamina all day long and your mood will improve too.
Its formula, which is wheat and dairy free and high in fiber, protein, antioxidants, omega-3 fatty acids and complex carbohydrates, might leave the impression that it must be a little too healthy to taste good.
Harvard researchers have found that consuming too much fructose--mainly as high fructose corn syrup from soft drinks and fruit punch--and eating too little complex carbohydrates and high-fiber foods like cereal, result in increased blood levels of C-peptide, a hormone that mirrors insulin levels and is linked to the development of type 2 diabetes.
These include simple sugars, like sucrose ([C.sub.6][H.sub.12][O.sub.6]), as well as the more complex carbohydrates. These compounds, which form an essential link in the chemical chain reactions of life, are created by autotrophic organisms--plants--that gather carbon and energy from the environment, carbon from carbon dioxide, and energy from sunlight.