CHAPTER II 

 CARBOHYDRATES 



The name carbohydrates is given to a class of bodies which are an 

 especially prominent constituent of plants and which are found also in 

 the animal body either free or as an integral part of various proteins. 

 They are called carbohydrates because they contain the elements C, H 

 and O; the H and being present in the proportion to form water. The 

 term is not strictly appropriate inasmuch as there are bodies, such as 

 acetic acid, lactic acid and inositol, which have H and present in the 

 proportion to form water, but which are not carbohydrates, and there 

 are also true carbohydrates which do not have H and present in this 

 proportion, e.g., rhamnose, CeH^Os- 



Chemically considered, the carbohydrates are aldehyde or ketone 

 derivatives of complex alcohols. Treated from this standpoint, the 

 aldehyde derivatives are spoken of as aldoses, and the ketone derivatives 

 are spoken of as ketoses. The carbohydrates are also frequently named 

 according to the number of oxygen atoms present in the molecule, e.g., 

 trioses, pentoses, and hexoses. 



The more common carbohydrates may be classified as follows: 



I. Monosaccharides. 



1. Pentoses, C 5 Hi 5 . 



(a) Arabinose. 



(b) Xylose. 



(c) Rhamnose (Methyl-pen tose), C 6 Hi 2 5 . 



2. Hexoses, CeH^Oe- 



(a) Glucose. 



(b) Fructose. 



(c) Galactose. 



II. Disaccharides, 



1. Maltose. 



2. Lactose. 



3. Iso-Maltose. 



4. Sucrose. 



III. Trisaccharides, 

 i. Rafnnose. 



