Biosynthesis of cellulose

This chapter discusses the biosynthesis of cellulose. It analyzes the older, fragmented literature and assesses its major contributions; concentrates extensively on new findings and coordinates their interpretations; and examines the existence of gaps in the knowledge of this complex process. The polymerization of D-glucan chains occurs by way of a multi-subunit, enzyme complex embedded in the plasma membrane. An almost simultaneous association, by means of hydrogen bonds, of the newly formed chains results in the formation of partially crystalline microfibrils. This mechanism of polymerization and crystallization results in the creation of microfibrils whose chains are oriented parallel (cellulose I). In A. xylinum, the complex is apparently immobile, but, in cells in which cellulose is deposited as a cell-wall constituent, it seems probable that the force generated by the polymerization of the relatively rigid microfibrils propels the complex through the fluid-mosaic membrane. The direction of motion may be guided through the influence of microtubules. The chapter discusses the cytological investigations of cellulose biosynthesis and elaborates the mechanism of polymerization.