Bakerian Lecture - The structure, function and synthesis of polysaccharides

Abstract

Cellulose is probably the most abundant organic compound occurring in nature, where it plays an all-important role in building up the skeletal framework of the plant cell wall. The accepted molecular structure of cellulose represented as repeating units of cellobiose was derived by chemical methods which I have previously summarized (Haworth 1939), and the constitution so assigned has received support in a remarkable way by the X-ray studies of Sponsler and Dore and of Meyer and Mark. The skeleton chain of cellulose can be illustrated by the model shown in figure 1, where four B-glucopyranose units are assembled side by side, such an arrangement being repeated many times to give a long extended chain structure. The arrangement is perfectly symmetrical since the hexagons are linked through the 1:4-positions, and the side chains, representing the primary alcohol groups at C6 of the glucose residues, lie alternately above and below the axis of the main chain. In this representation each alternate hexose is rotated through 180° so that deviation from the linear structure is almost completely obviated. The constitution is in keeping with the fact that cellulose occurs in fibrous form and is highly resistant to solvent action and to chemical attack. It is suggested that there are possibly some infrequent points of bonding between adjoining chains to provide a kind of cross-linkage.