Carbohydrates in cell surfaces.

TLDR: The carbohydrate components of cell surfaces occur in structures that are free to react with agents in the external environment of the cell, as in the antigenic reactions in which they are involved.

Abstract: Publisher Summary The carbohydrate components of cell surfaces occur in structures that are free to react with agents in the external environment of the cell, as in the antigenic reactions in which they are involved. Carbohydrates are well suited for formation of stereospecific structures. They are relatively rigid molecules in which there are many groups for hydrogen bonding and for lipophilic interaction. The shape of the molecule and the position of the reactive groups can be markedly different depending on the sugars involved, the hydroxyl position to which the nonreducing sugar is linked, and the α or β configuration of the glycosidic linkage. Glucose is rarely in the outer tier of sugars in glycoproteins or glycolipids. This is consonant with the recognition site hypothesis, because free glucose in the body fluids could otherwise inhibit recognition of specific binding or receptor sites. Sialoglycoproteins are generally poor antigens, and antibodies against glycoproteins are rarely directed toward the sialic acids, even though they are terminal sugars in glycoproteins and glycolipids.