4 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



1. Monosaccliarides (C 6 H 12 6 ). The most important members of this 

 group are : 



Dextrose. 

 Levulose. 



Galactose. 

 Mannose. 



2. Disaccharides (C 12 H 22 O n ). The most important members of this 

 group are : 



Cane Sugar, 

 Lactose. 



Maltose. 

 Isomaltose. 



3. Polysaccliarides (C 6 H 10 6 ) n . The most important members of this 

 group are : 



Starch. | Cellulose. 



Glycogen. 

 Dextrins. 



Tunicin. 

 Gums. 



Inulth. 



The monosaccharides. When an alcohol is oxidised, the first 

 stage in oxidation is the formation of an aldehyde, or a ketone ; if 

 oxidation of the aldehyde is continued, an acid is formed. 



When more complicated alcohols are oxidised, similar products result. 

 The monosaccharides are the first oxidation products of the hexatomic 

 alcohols (CH 2 .OH (CH.OH) 4 CH 2 OH). 



Of the hexatomic alcohols, three are known, namely sorbite, mannite, 

 and dulcite. 



Dextrose is the aldehyde of sorbite. 1 

 Mannose ,, mannite. 



Galactose dulcite. 



Levulose ketone of mannite. 



Sugars of the monosaccharide group may thus be either aldehydes, 

 when they are called aldoses ; or ketones, when they are called ketoses. 



Dextrose, mannose, and galactose are aldoses, and have the structure 

 represented by the following formula : 



CH 2 .OH (CHOH) 4 CHO 



They differ from one another in their stereochemical formulae. 

 Levulose is a ketose, and has the structure represented by 



CH 2 .OH (CH.OH.) 3 CO CH. 2 OH 



The difference between the aldoses and ketoses is shown by oxidation, 

 levulose, like all ketoses, yielding acids which are poorer in carbon. 



If chlorine or bromine water is used as the oxidising agent, the 

 aldoses (dextrose, mannose, and galactose) give isomeric monobasic acids 

 of the formula 



CH 2 .OH (CH.OH) 4 COOH ; 



and then, by further oxidation by means of nitric acid, yield dibasic 

 acids of the formula 



COOH (CH.OH) 4 COOH 

 Both sets of acids are stereo-isomerides. 



Monobasic acid. Dibasic acid. 



From Dextrose . . Gluconic acid Saccharic acid. 



Mannose . . Mannonic acid Manosaccharic acid. 



Galactose . . Galactonic acid Mucic acid. 



1 JVleunier, Compt. rend. Acad. d. sc.. Paris, tome cxi. p. 49 ; Vincent and Delachanal, 

 Hid., p. 51. 



