78 



THE CARBOHYDRATES 



the number of carbon atoms in their molecules, those contain- 

 ing five being called pentoses, while those containing six atoms 

 are known as hexoses. For this reason the use of the terms 

 monose and biose in place of monosaccharide and disaccharide 

 is to be deprecated owing to the confusion which is liable to 

 result therefrom. 



A scheme for the classification of the carbohydrates is 

 given below: — 



Trioses (CgHgOg) 

 Tetroses (C4H8O.J) 

 Pentoses (C5H10O5) 



bose, Apiose. 

 Methyl pentoses (CgHijO^) 



Quinovose. 



Arabinose, Xylose, Ri- 

 Rhamnose, Fucose, 



Monosaccharides • 



Hexoses (CgHjjOg) 



f Aldoses : Glucose, Man- 

 j nose. Galactose. 

 ] Ketosea : Fructose, Sor- 

 ( bose 

 Sedoheptose, Mannoketo- 



Sugars 



Disaccharides ■ 



Heptoses (C,Hi40,) 



heptose. 

 Glucoxyloses (CiiHjnOio). Primeverose, 



Strophanthobiose, Vicianose. 

 (C12H22O11). Sucrose, Lactose,* Maltose, Iso- 

 maltose, Gentiobiose, Cellobiose, Treha- 

 lose, Melibiose, Turanose. 

 Trisaccharides (C^gH^gOig). Raffinose, Melicitose, Gentianose. 

 Tetrasaccharides (€,41142021). Stachyose. 

 Unknown constitution : Agavose, Lupeose. 



Non-sugars or 

 Polysaccharides 



Pentosans (C5Hg04)n 



Hexosans (CgHuOs)!! 



Araban, Xylan. 



Glucosans : Starch, Dextrin, Gly- 

 cogen, Lichenin, Cellulose. 



Fructosans : Inulin, Graminin, 

 Phlein, Triticin. 



Mannans. 



Galactans. 



T^ . , T, u J i ^ Hemicelluloses. 

 Derived carbohydrates ^ _ 



containing -COOH Mucilages. 

 and other groups ( p^^^.^ Lbstances. 



SOLUBILITIES OF THE CARBOHYDRATES. 



As might be expected of a group of substances of such 

 varying complexity and widely different function in the plant, 

 the solubilities of the carbohydrates present a considerable 

 range of variation, some idea of which can be obtained from 

 the following facts : — 



I. Readily soluble in water or dilute alcohol, but insoluble 

 in absolute alcohol and other organic solvents, e.g. sugars, 

 inulin. 



* Not found in the vegetable kingdom. 



