66 PHYSIOLOGY 



Thus glucose COH(CHOH),CHOH.CHOH.CH 2 OH becomes 

 CHOH . (CHOH) 2 . CH . CHOH . CH 2 OH 



This change in the arrangement of the molecule renders a further stereoisomerism 

 possible, owing to the fact that now the end group which was formerly COH becomes 



H 



O 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 C OH OH C H 



HOCH 



HCOH 



or 



HOCH 



HCOH 



CH 2 OH CH 2 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 formulas of which would ba represented as follows : 



H C OCH 3 CH 3 C, 



HCOH \ HCOH 



HOCH S" HOCH 



HCOH 



HCOH 



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 a glucoside of glucose, lactose as the ft galac- 

 toside of glucose. The mode of combination of the two hexose groups to form these 

 disaccharides may be represented as follows : 



H H OH H H 



CH 2 OH C C C C C glucose rest 

 OH V HOH 



maltose. 



HO H HO HO 

 OHC C C C C CH 2 glucose rest 

 H OH H H 



