The building units

Abstract

Carbohydrate building units usually have cyclic structures — which means that their component atoms are joined in a way that forms a closed ring. One of the ring atoms is almost always oxygen and the remaining atoms are carbon. To understand the shapes of the very many different units which exist in natural polymers, it is helpful to classify them according to the number of atoms involved in this ring; this number may be seven, six, five or zero (Fig. 2.1).