Glucose, not cellobiose, is the repeating unit of cellulose and why that is important

Abstract

Despite nomenclature conventions of the International Union of Pure and Applied Chemistry and the International Union of Biochemistry and Molecular Biology, the repeating unit of cellulose is often said to be cellobiose instead of glucose. This review covers arguments regarding the repeating unit in cellulose molecules and crystals based on biosynthesis, shape, crystallographic symmetry, and linkage position. It is concluded that there is no good reason to disagree with the official nomenclature. Statements that cellobiose is the repeating unit add confusion and limit thinking on the range of possible shapes of cellulose. Other frequent flaws in drawings with cellobiose as the repeating unit include incorporation of O-1 as the linkage oxygen atom instead of O-4 (the O-1 hydroxyl is the leaving group in glycoside synthesis). Also, n often erroneously represents the number of cellobiose units when n should denote the degree of polymerization i.e., the number of glucose residues in the polysaccharide.