ABSTRACT
Carbohydrates are the most abundant biomolecules produced on the earth; photosynthetic plants and algae convert over 100 billion metric tons of C 0 2 and H20 into sugars, starches, and cellulose-like substances. These are polyhydroxy aldehydes or ketones and their derivatives or sub stances that yield such compounds on hydrolysis. Most carbohydrates have the empirical formula (CH20 )n; some do not conform to it, while others contain in addition to C, H, and O, elements such as nitrogen, phosphorus, or sulfur. Three major size classes of carbohydrates are monosac charides, oligosaccharides, and polysaccharides, the word saccharide meaning sugar. Mono saccharides are simple sugars consisting of a single polyhydroxy aldehyde or ketone unit; oligosaccharides consist of short chains of few (two to eight) monosaccharide units joined together by characteristic glycosidic linkages. The most abundant monosaccharide and disaccha ride found in nature are glucose (fruit sugar) and sucrose (cane sugar). The latter consists of two 6-carbon sugars, D-glucose and D-ffuctose joined covalently. All common mono-and disaccha rides have names ending with the suffix “-ose”. Most oligosaccharides do not occur as free enti ties but are joined to nonsugar molecules such as lipids or proteins (glucoconjugates). The poly saccharides are the high-molecular-weight, long-chain compounds containing hundreds or thousands of monosaccharide units, either in linear or branched chain fashions. The most abun dant polysaccharides found in nature are starch and cellulose, which consist of recurring units of D-glucose but differ in the type of glucosidic linkage (1).
