Microfibrils biosynthesis

Naturally occurring cellulose is extremely mechanically stable and is highly resistant to chemical and enzymatic hydrolysis. These properties are due to the conformation of the molecules and their supramolecular organization. The unbranched pi 4 linkage results in linear chains that are stabilized by hydrogen bonds within the chain and between neighboring chains (1). Already during biosynthesis, 50-100 cellulose molecules associate to form an elementary fibril with a diameter of 4 nm. About 20 such elementary fibrils then form a microfibril (2), which is readily visible with the electron microscope. 

The primary cell-wall of plants is formed by microfibrils of cellulose in a complex matrix of polysaccharides, proteins, and glycoproteins. The structure and relationship of the different components is under continuous study and revision, and most of them can now be identified and their biosynthesis studied.124"126... 

The preceding, brief discussion about the complex structure of the cell walls and the fine features of the cellulosic microfibrils clearly indicates that the formation and functioning of this system must involve not only the chemical synthesis of the raw materials, but also other fundamental processes, such as the packing of the cellulose molecules in the microfibrils and the orientation of the microfibrils within the cell walls. These complex processes are so closely related in biological processes that a discussion of one aspect without consideration of others would be rather meaningless. However, for the sake of convenience and simplicity, the biosynthesis of cellulose, or the process of polymerization of the D-glucose residues, will be considered first, irrespective of the physical structure of the final product. 

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