50 CHEMISTRY OF PLANT LIFE 



Sucrose is a non-reducing sugar, forms no osazone, and is 

 not directly fermentable by yeast, although most species of yeasts 

 contain an enzyme which will hydrolyze sucrose into its component 

 hexoses, which then readily ferment. 



When hydrolyzed by acids, or by the enzyme " invertase," 

 it yields a mixture of equal quantities of glucose and fructose. 

 Sucrose is dextrorotatory, but since fructose has a greater specific 

 rotatory action to the left than glucose has to the right, the 

 mixture resulting from the hydrolysis of sucrose is levorotatory. 

 Since the hydrolysis of sucrose changes the rotatory effect of the 

 solution from the right to the left, the process is usually called the 

 " inversion " of sucrose, and the resultant mixture of equal parts 

 of glucose and fructose is called " invert sugar." As has been 

 pointed out, solutions of invert sugar become optically inactive 

 when heated to 82 C., because of the reduction in the rotatory 

 power of fructose due to the higher temperature. 



The probable linkage of the two hexoses to form sucrose, in 

 such a way as to produce a non-reducing sugar, is illustrated in 

 the following formula: 



i O r 



CH 2 OH - CHOH CH - CHOH - CHOH - CH 



A 



CH 2 OH - CHOH - CHOH CH C - CH 2 OH 



Y 



Trehalose seems to serve as the reserve food for fungi in much 

 the same way that sucrose does for higher plants. It is composed 

 of two molecules of glucose linked together through the aldehyde 

 group of each, as trehalose is a non-reducing sugar. This linkage 

 is illustrated in the following formula: 



O 



CH 2 OH CHOH CH CHOH CHOH - CH 



O 

 CH 2 OH CHOH - CH - CHOH CHOH - CH 



I o ! 



