Important Terms (Glycoconjugates and Carbohydrates)

Aglycone Group attached to the hydroxyl of a furanose or pyranose sugar to form a glycoside. Can vary from a simple methyl group to other sugars to complex alkaloids.

Aldose Polyhydroxy aldehyde with three or more carbon atoms. When of sufficient length will form five-or six-membered ring (furanose or pyranose) hemiac-etals. Designated d- or l- based on the configuration of the asymmetric center furthest from the carbonyl group relative to glyceraldehyde.

Anomer Formation of the cyclic ring structure confers asymmetry on the original carbonyl carbon atom. The two anomers produced are alpha- (the newly formed hydroxyl group projects on the same side as the five- or six-membered ring) or beta- (the new hydroxyl projects on the opposite side of the newly formed ring). This is combined with D-, or L-; a-D-glucopyranose, j-L-fructofuranose, for example.

Epimer Saccharide that differs from a reference sugar at a single asymmetric center. Thus, D-galactose is the 4-epimer of D-glucose.

Furanose Five-membered ring (derived from furan) with a single oxygen formed by reaction of the carbonyl carbon of an aldose or ketose with the appropriate hydroxyl group. Sugars commonly found as furanoses include ribose and 2-deoxyribose (in RNA and DNA, respectively), and fructose in combined form (sucrose, for example).

Glycolipid Structure containing one or more saccharide units covalently attached to the primary hydroxyl group of N-acyl sphingosine (ceramide), a C-18 amino alcohol. Those containing sialic acid are termed ganglio-sides.

Glycoprotein Protein with covalently attached saccharides. Linkage may be N- (amide nitrogen of aspara-gine residues), or O – (serine and threonine are most common). The saccharide units may be heterogeneous within the same protein, even at the identical substitution site.

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