Alpha linkages

The main raw material required for the production of viscose is ceUulose (qv), a natural polymer of D-glucose (Fig. 1). The repeating monomer unit is a pair of anhydroglucose units (AGU). CeUulose and starch (qv) are identical but for the way in which the ring oxygen atoms alternate from side to side of the polymer chain (beta linkages) in ceUulose, but remain on the same side (alpha linkages) in starch. 

The carbohydrate class, polysaccharide, represents compounds in which the molecules contain many units of monosaccharides joined together by glycoside links. Upon complete hydrolysis, a polysaccharide delds monosaccharides. Starch is the most valuable polysaccharide. The starch molecules (amylose and anylopectin) are tree-like, containing 250 to 1000 or more glucose units per molecule joined together through alpha linkages. 

Has the alpha linkage of the galactose units been established ... 

I believe that it has been established from two standpoints. First, a galac-tosylmannose disaccharide on hydrolysis changes in rotation so as to suggest the presence of an alpha linkage. Secondly, the galactosyl units are split from the disaccharide and in some instances from the i>olysaccharide by means of a proved a-galactosidase. 

As soon as it is involved in a glycosidic link, it is locked into one form or the other. Starch has one form (alpha linkage) and cellulose the other (beta), and enzymes will discriminate absolutely between the two. So we cannot digest cellulose. Even cows cheat because it is not their enzymes that break down the cellulose from grass, but the tanks of bacteria they carry with them ... 

Cellulosic adhesives - Cellulose is a naturally occurring water insoluble polymer which is a major component of plants - wood is 60% cellulose. It is a polysaccharide very similar to starch except that the saccharide imits of the macromolecules are eonnected by beta-linkages in contrast to the alpha linkage for starch. Cellulose ean be reacted with various acids to produce water soluble adhesives such as methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose, or organic solvent soluble polymers such as hydroxypropylcellulose and cellulose acetate. The polymers have molecular weights of about 25,000 and are used for adhesives in paper, textile, plastic, and leather shoes. 

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