84 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



occurring groups are generally related. The mono-saccharoses 

 can evidently be considered as built up by the combination 

 of a number of molecules of formaldehyde. By elimination of 

 water from two or more molecules of mono-saccharoses, a 

 di-saccharose results, and by further elimination of water 

 poly-saccharoses are obtained. Among the more important 

 members of these various groups may be mentioned, among 

 the saccharoses, grape sugar or glucose, and fruit sugar or 

 Icevulose ; among the di-saccharoses, cane sugar (or beet sugar, 

 which has the same composition) and milk sugar ; among the 

 poly-saccharoses, starch and cellulose. 



Our knowledge of the molecular structure of carbohydrates 

 is naturally greatest in regard to the simplest group, viz., the 

 mono-saccharoses, and inasmuch as sugars belonging to this 

 group are produced by the addition of the elements of water 

 to both di-saccharoses and poly-saccharoses, it is evident 

 that a knowledge of the simpler substances must be of great 

 help towards the ultimate unravelling of the much more 

 complicated chemistry of such substances as starch and 

 cellulose. We may, therefore, proceed to consider the 

 general properties of the carbohydrates of this group. 



Mono-saccharoses. The members of this group of 

 carbohydrates may be described as the first oxidation products 

 of alcohols containing more than one carbon atom each of 

 which has an OH group attached. 



The simplest alcohol is of course methyl alcohol, HCH 2 OH, 



H 



its first oxidation product is fwmaldehyde, \ /H, and, as 







already stated, formaldehyde is the simplest carbohydrate, 

 and may be looked upon as the basal substance of the sugars, 

 although it does not itself exactly fall within the above 

 definition of a mono-saccharose. 



