THE COMPONENTS OF PLANTS AND ANIMALS II 



left. On account of this fact, this breaking up of cane sugar 

 has been called inversion and the use of this term has been 

 extended to designate in general the hydrolytic cleavage of di- 

 saccharids into their constituent monosaccharids. 



Lactose. Lactose, or milk sugar, is a characteristic ingredi- 

 ent of the milk of mammals. Like sucrose, it may be broken 

 up, with the addition of one molecule of water, into two mole- 

 cules of monosaccharids, in this case dextrose and galactose. 

 It is less soluble than sucrose and therefore less sweet to the 

 taste, having a gritty feel in the mouth. It is not found in 

 plants. 



Maltose. By the action of certain ferments upon starch 

 during the germination of seeds and also in the digestive tract 

 of animals, a disaccharid known as maltose is produced. It is 

 therefore present abundantly in malt, whence its name. This 

 sugar when hydrolyzed yields two molecules of dextrose. 



13. General properties. The disaccharids are crystalline, 

 soluble in water and optically active. Sucrose does not reduce 

 an alkaline copper solution, but lactose and maltose do. The 

 disaccharids are not fermentable. Any cases in which they are 

 apparently fermented are found to be preceded by some action 

 which inverts or breaks up the disaccharids into their con- 

 stituent monosaccharids. 



Trisaccharids 



14. By the union of three molecules of CeH^Oe with the 

 elimination of two molecules of water, there may be formed 

 the compound CigH-BOie, called a trisaccharid. One such, 

 known as raffinose, is present in the sugar beet, the cotton seed, 

 in barley and in wheat. Upon hydrolysis it yields one mole- 

 cule each of dextrose, levulose and galactose. 



Polysaccharids 



15. Chemical structure. The polysaccharids, like the di- 

 saccharids, are anhydrids, but are formed by the combination of 

 many molecules of the monosaccharids and have a correspond- 

 ingly high molecular weight. The general formula of the hexose 

 polysaccharids is (C 6 H 10 O 5 )n, the value of n doubtless varying 



