72 



PHYSIOLOGY 



stereoisomerism possible, owing to the fact that now the end group 

 which was formerly COH becomes 



H 

 C OH 



C 



so that now there are five instead of four asymmetric carbon atoms. 

 The two isomers of glucose, which are thus rendered possible, are 

 represented by the following structural formulae : 



H O- OH OH a H 



or 



HCOH 



HCOH 



CH 2 OH 



CH.OH 



In these molecules the OH attached to the end group can be replaced 

 by other radicals, including other sugar molecules. In this way we 

 get the formation of glucosides. Thus, if glucose be dissolved in 

 methyl alcohol and be treated with hydrochloric acid, we obtain a 

 and /3 methyl glucosides, the formulae of which would be represented 

 as follows : 



H OCH 



CH,0 C H 



CH 2 OH 



CH 2 OH 



Instead of methyl we might insert other groups, and even other hexose 

 groups, such as glucose or galactose, obtaining the two sugars maltose 

 and lactose, which may thus be regarded as glucosides maltose as the 



