Among disaccharides, saccharose, maltose and lactose are known
better. Saccharose, known also as cane-sugar, consists of two connected
monosaccharides — glucose and fructose. Maltose contains two residues
of D-glucose, while lactose contains D-glucose and D-galactose. Lactose is
found in milk and is called milk-sugar.
Raffinose is a representative of trisaccharides. Large quantity of it is
found in sugar beet. It consists of fructose, glucose and galactose residues.
Polysaccharides (also called glycans) are high-molecular compounds
with single or branched chains. They can be built of equal monosaccharide
units (homopolysaccharides). They are subdivided into structural and
reserve.
Figure 2–51. Binding of monosaccharides and formation of di- and polysaccharide chains.
Cellulose and chitin are the most spread structural polysaccharides.
Cellulose is widely spread in the plant kingdom. It participates in building
the wood, cotton fibres, cell walls of different lower and higher organisms. It
consists only of D-glucose residues. Chitin serves as a basic structural
element of the outer solid coat of most insects and crustacea, as well as a