28 PHYSIOLOGICAL CHEMISTRY 



H 



0=0 



H C OH 

 HO C H 

 H C OH 

 H C OH 



CH 2 OH 



Glucose 



An example of a sugar containing a ketone group is fructose, 

 which has the following formula: 



CH 2 OH 



c=o 



HO C H 



H C OH 



I 

 H C OH 



I 

 CH 2 OH 



Fructose 



Many of the reactions characteristic of the carbohydrates de- 

 pend upon the properties of the aldehyde or ketone groups 

 which they contain. In the case of the more complex carbo- 

 hydrates, these reactive groupings are usually combined in such 

 a way that they do not show their characteristic behavior. 



Optical Activity. On inspecting the above formulae for 

 glucose and fructose it will be observed that the hydrogen and 

 hydroxyl groups of the four carbon atoms occupying the middle 

 portion of the chain are not arranged in a regular manner. 



