Alginate is a polysaccharide, like starch and cellulose. It is composed of several building units (typically 100–3000) linked together in a flexible chain. Long molecules constructed from identical or nearly identical building units are called polymers, while the building units themselves are called monomers. Polymers of natural origin are commonly called biopolymers.
Alginate is built upon the basis of two sugars, which are both uronates, the salts of mannuronic and guluronic acid. When producing alginates, uronic acid is converted into the salt-forms mannuronate (M) and guluronate (G). See Figure 4.