PRACTICAL PHYSIOLOGY. 



[IIL 



acid. This is a process of hydrolysis. They are less soluble in 

 alcohol the more concentrated it is. In absolute alcohol (and 

 ether) almost all the carbohydrates are soluble with difficulty, or 

 insoluble. 



(h.) When strongly heated they are decomposed, charred, and 

 yield a variety of products. Inosite, which, however, is not a true 

 carbohydrate, alone undergoes partial sublimation {Tollens). 



Classification of some Carbohydrates : — 



The + and - signs indicate that, as regards polarised light, the substances 

 are dextro- and Isevorotatory respectively. 



The amyloses are anhydrides of the glucoses [^^(^6^12^6) " 

 nW^O = (C^jH^qO^),,], Avhile the saccharoses are condensed glucoses 

 (CgHigOg + CjjHigOg - H2O - CjoHo^Ou)]. The saccharoses are 

 converted into glucoses on boiling with dilute sulphuric acid. 



Emil Fischer has shown that the monosaccharids are aldehydes 

 or ketones of a hexatomic alcohol, Cj.Hg (OH)^. Just as aldehyde 

 CoH^O is formed by oxidising ethylic alcohol C2H^0, so from 

 raannitic alcohol the simplest carbohydrate C^-HjoO,, is formed. 

 When two molecules of such monosaccharids polymerise with the 

 loss of water, they form the disaccharids, which may spht up 

 again and yield monosaccharids. When there is further poly- 

 merisation with loss of water we get bodies with molecules of 

 larger size — the simpler members being dextrins, the more complex 

 starch and glycogen, forming the group of polysaccharids. These in 

 turn may break down and yield monosaccharid or disaccharid 

 molecules. Thus the transformation imdergone by carbohydrates 

 in the organism, their conversion from one form to another, are 

 rendered more easy of comprehension. 



