What are the four kinds of saccharides?
The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates.
They are aldehydes or ketones with two or more hydroxyl groups. The general chemical formula of an unmodified monosaccharide is (C•H2O)n, literally a "carbon hydrate". Monosaccharides are important fuel molecules as well as building blocks for nucleic acids. The smallest monosaccharides, for which n=3, are dihydroxyacetone and D- and L-glyceraldehydes
Two joined monosaccharides are called a disaccharide and these are the simplest polysaccharides. Examples include sucrose and lactose.
They are composed of two monosaccharide units bound together by a covalent bond known as a glycosidic linkage formed via a dehydration reaction, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C12H22O11
An oligosaccharide is a saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars).
Oligosaccharides can have many functions including cell recognition and cell binding. For example, glycolipids have an important role in the immune response.
Polysaccharides are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages, and on hydrolysis give the constituent monosaccharides or oligosaccharides.
They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.