THE CARBOHYDRATES AND THEIR METABOLISM 223 



O 

 // 



a 



*HCOH 

 *HCOH 



*HCOH 



I 

 CII 2 OH 



Accordingly there may be 2 4 or 16 possible aldohexoses. Largely through 

 the researches of Emil Fischer, 14 of these are now known, although only 

 three glucose, mannose, galactose occur naturally. These isomers are 

 represented in Table II. 



TABLE II. ALDOHEXOSES 

 1. Mannitol Series 



All sugars known as rt-sugare are not necessarily dextrorotatory, nor are all 

 1-sugars neciarilv levorotatory." All co m ,x,nd lerivl from ^uco^ by r^ctiona 

 that leave the stereochemical structure unchanged an- designated d-compounda, r 

 gardless of their rotation, and similarly for 1-forms. 



