Homoglycans

Homoglycans are a class of complex carbohydrates composed of only one type of monosaccharide repeating unit. This contrasts with heteroglycans, which are made up of two or more different monosaccharide units. The repeating monosaccharide in a homoglycan can be a simple sugar like glucose or fructose, or a modified sugar like N-acetylglucosamine.

The structure of homoglycans is defined by the specific monosaccharide and the type of glycosidic linkage between the repeating units. For example, starch and glycogen are both homoglycans made of glucose, but they differ in the arrangement of their glycosidic bonds, leading to different branching patterns and properties. Cellulose, also a homoglycan of glucose, has a linear structure with beta-glycosidic linkages that provides rigidity.

Homoglycans play diverse biological roles. Starch and glycogen serve as energy storage molecules in plants and animals, respectively. Cellulose is a major structural component of plant cell walls. Other homoglycans, such as chitin (a homoglycan of N-acetylglucosamine), provide structural support in the exoskeletons of insects and crustaceans, as well as in fungal cell walls. The specific arrangement and linkage of the monosaccharide units dictate the physical and chemical properties, and consequently, the biological function of each homoglycan.