CARBOHYDRATES 149 



III. Amy loses or Polysaccharids, n(C 6 H 10 O 6 ). 

 -|- Starch (paste). 

 + Dextrin. 

 + Glycogen. 



Cellulose (insoluble in water). 



The sugars of the first class are characterized by the readiness 

 with which they take up oxygen from their surroundings and 

 thus reduce bodies rich in oxygen. Upon this fact depend some 

 of the most important tests for their recognition, viz., the reduc- 

 tion of alkaline metallic solutions. The monosaccharids are fur- 

 ther characterized by their susceptibility to the action of yeast- 

 cells, being broken down by the enzymes of these organisms 

 into alcohol apd carbon dioxide. 



The disaccharids do not all reduce alkaline metallic solutions. 

 They may, however, be transformed into monosaccharids by boil- 

 ing with dilute acids. They thus undergo a hydrolytic cleavage, 

 commonly termed inversion, in which process they are transformed 

 into glucoses. Two molecules of a monosaccharid can be obtained 

 from one hydrated molecule of a disaccharid. Their relations 

 may be shown thus : 



Cane-sugar -f H 2 O = dextrose -f levulose 

 Maltose -f H 2 O = dextrose -f dextrose. 



It will be observed that the sugars are included in the first two 

 classes : they are either glucoses or saccharoses. The third class, 

 or amyloses, may be regarded as the anhydrides of the glucoses. 

 They are called polysaccharids because their molecules are made 

 up of a multiple number of glucose molecules minus an equal num- 

 ber of molecules of water [n(C 6 H 12 O 6 )- n(H 2 O)= n(C 6 H 10 O 5 )]. 

 Glucoses may be obtained from some of the amyloses by hydro- 

 lysis, accomplished either by boiling with dilute acids or by the 

 action of an enzyme. In the formation of dextrose from starch 

 various intermediate products appear, such as soluble starch (amy- 

 lodextrin), different varieties of dextrin, maltose and isomaltose.. 

 Most of those celluloses which occur in the cell walls of the ordi- 



