CARBOHYDRATES 



55 



yeast, Saccharomyces ellipsoideus, exhibits the opposite preference 

 for these acids. 



These observations upon some of the earlier known forms of 

 optically active organic acids led the way to a general study of 

 this phenomenon as exhibited by the optically active soluble car- 

 bohydrates. The results of these studies may be considered in 

 connection with the several different types of reactions which 

 these sugars undergo, as follows: 



Glucoside Hydrolysis. As was pointed out in connection with 

 the discussion of the mutarotation of glucose, this sugar may exist 

 in either the a or the |8 modification. Glucosides of both a and 

 glucose are of common occurrence. The difference in molecular 

 configuration, in such cases, may be represented by the following 

 formulas: 



C H 

 H C OH 

 CH 2 OH 



o-Glucoside 



H C R 



H C OH \ 



HO C H 



0-Glucoside 



The radical represented by the R may be either a common 

 alkyl radical (as CHs, C2Hs, etc.), another saccharide group (as 

 in the case of the disaccharides, trisaccharides, etc.), or some other 

 complex organic group (as in the case of the natural glucosides 

 described in Chapter VI). But, in every case, the glucoside is 

 easily hydrolyzed by the enzyme maltose (or a-glucase) if the 

 molecular arrangement is that represented by the a-attachment, 

 ^or by the enzyme emulsin (or /3-glucase) if the glucoside is of the 

 /3 type; but emulsin is absolutely without effect upon a-glucosides, 

 and maltase does not produce the slightest change in ^-glucosides. 

 These statements hold true regardless of the nature of the group 

 which is represented by the R in the formulas above. Hence, the 



