Question: what are the structural differences among the three classes of carbohydrates?
Answer: On the basis of the number of forming units, three major classes of carbohydrates can be defined: monosaccharides, oligosaccharides and polysaccharides. Monosaccharides or simply sugars are formed by only one polyhydroxy aldehydeidic or ketonic unit. The most abundant monosaccharide is D-glucose, also called dextrose.