Sugars Monosaccharides

Fig. 3-11 Carbohydrates in (a) 3-, 5-, and 6-carbon sugars (monosaccharides), (b) oligosaccharides, and (c) polysaccharides. (Reprinted with permission from W. K. Purves and G. H. Orians, "Life The Science of Biology," pp. 63-81, Copyright 1987 by Sinauer Associates, Inc., Simderland, MA.)...

Carbohydrate a general term for a class of molecules of composition C H2nO , including the simple sugars (monosaccharides), oligosaccharides, and polysaccharides. 

The carbohydrates are a group of naturally occurring carbonyl compounds (aldehydes or ketones) that also contain several hydroxyl groups. The carbohydrates include single sugars (monosaccharides) and their polymers, the oligosaccharides and polysaccharides. 

The sugars (monosaccharides) occur in the metabolism in many forms (derivatives). Only a few important conversion reactions are discussed here, using D-glucose as an example. 

A glycoside can be formed with aliphatic alcohols, phenols, and hydroxy carboxylic acids, but the most important glycosides are those formed with other sugars. Monosaccharides are linked by glycosidic bonds to form disaccharides (fig. 12.8). For instance, the disaccharide maltose contains a glycosidic bond between the C-l of one glucose molecule and the C-4 of another. The compound is said to... 

Nucleotide sugars Monosaccharides Bacteria, archaea and eukaryotes ... 

Classify carbohydrates as aldoses, ketoses, D or L sugars, monosaccharides, or polysaccharides. 

The simplest carbohydrates are called monosaccharides or simple sugars. Monosaccharides have three to seven carbon atoms in a chain, with a carbonyl group at either the terminal carbon (Cl) or the carbon adjacent to it (C2). In most carbohydrates, each of the remaining carbon atoms has a hydroxy group. Monosaccharides are usually drawn vertically, with the carbonyl group at the top. 

Carbohydrates are polyhydroxy aldehydes and ketones. They are classified according to the number of carbon atoms and the kind of carbonyl group they contain. Glucose, for example, is an aldohexose, a six-carbon aldehy-dic sugar. Monosaccharides are further classified as either D or L sugars, depending on the stereochemistry of the chirality center farthest from the carbonyl group. 

The commission then turned to nomenclature for the constituents of the glucides, subdividing them into nonhydrolyzable reducing sugars (monosaccharides) and into substances split by hydrolysis into one or more reducing sugars, accompanied or not by other substances. 

Examples include sugars (monosaccharide, di- and polysaccharides), starches, and cellulose. Carbohydrates are used as an energy source by organisms, and most are formed by green plants and are obtained by animals via food intake. 

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