Mammalian Macromolecular Carbohydrates: Classification and Some Names

H istochemically detectable carbohydrates occur as large molecules on the outside surfaces of all types of cell, as stored or secreted substances within some cells, and in the extracellular matrix. They are all macromolecules in which sugar units (monosaccharides) are joined in chains. Some of the structural features of sugars are summarized in Figure 1, which also shows an abbreviated nomenclature that is commonly used to show how the units are connected by glycoside linkages. The classification of macromolecular carbohydrates can be quite complicated because it has to take into account materials as diverse as cellulose, gastric mucus and cartilage matrix (1-4). The scope of this article is restricted to those macromolecular carbohydrates of mammalian tissues that can be stained by methods that provide information about chemical structure