A glycosidic bond is formed between the hemiacetal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some organic compound such as an alcohol. If the group attached to the carbohydrate residue is not another saccharide it is referred to as an aglycone. If it is another saccharide, the resulting units can be termed as being at the reducing end or the terminal end of the structure. This is a relative nomenclature where the reducing end of the di- or polysaccharide is towards the last anomeric carbon of the structure, and the terminal end is in the opposite direction.
In the literature, the bond between an amino group or other nitrogen-containing group and the sugar is often referred to as a glycosidic bond (although IUPAC seems to suggest that the term is a misnomer). For example, the sugar-base bond in a nucleoside may be referred to as a glycosidic bond.[1] A substance containing a glycosidic bond is a glycoside.
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Carbohydrates
Formerly the name "carbohydrate" was used in chemistry for any compound with the formula Cm (H2O) n. Following this definition, some chemists considered formaldehyde (CH2O) to be the simplest carbohydrate,[3] while others claimed that title for glycolaldehyde.[4] Today the term is generally understood in the biochemistry sense, which excludes compounds with only one or two carbons.
Natural saccharides are generally built of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. A typical monosaccharide has the structure H-(CHOH)x(C=O)-(CHOH)y-H, that is, an aldehyde or ketone with many hydroxyl groups added, usually one on each carbon atom that is not part of the aldehyde or ketone functional group. Examples of monosaccharides are glucose, fructose,
