Fig. 5 Variation of glucose polymers. By the presence of variable linkage patterns, i.e., a1-4/6, b1-3/4/6, different types of naturally occurring glucose polymers (glucans) are generated, of which biological functions are distinct. For example, a1-4 glucan (amylose) is soluble and an essential energy source, while b1-4 glucan (cellulose) forms a mechanically stable insoluble fiber hardly digested by most organisms.