Monosaccharides are the simplest form of carbohydrates. They may be classified based on the number of constituent carbon atoms. For instance, hexose is a monosaccharide with six carbon atoms. They may be further classified based on the functional group present. An aldose is a sugar with an aldehyde functional group whereas a ketose is a sugar with a ketone functional group. [[[Idose]] is one of the hexose monosaccharides and it belongs to the aldoses.
Idose is isomeric with galactose. Galactose is an aldohexose similar to glucose in terms of chemical structure. This means that they have similar chemical formula: C6H12O6. Galactose does not occur in free state and it is usually found as a constituent of complex biomolecules (e.g. lactose, galactan). Similarly, idose has not been found in nature in its free form. It is a component of glycosaminoglycans: dermatan sulfate and heparan sulfate. The uronic acid analog of idose is iduronic acid. The L-iduronic acid is the major uronic acid component of dermatan sulfate and heparin.
The L-idose is epimeric with D-glucose at C5.