32 



SCIENCE PROGRESS 



body possesses means of dealing with other simple carbohydrate 

 molecules. Hexose sugars isomeric with dextrose can suffer 

 metabolism. Fructose, mannose and galactose, for example, 

 are broken down in the body and, as a preliminary to further 

 change, can be converted into glycogen, the first-named sugar 

 almost as readily as dextrose itself. Now, the glycogen molecule 

 is an aggregate of a number of dextrose molecules and would 

 appear to be always the same substance, whatever simple 

 sugar has acted as its precursor. The physiological occurrence 

 of such a moulding of sugar molecules as this betokens raises 

 chemical considerations of no small interest. The biochemist 

 would miss his vocation if he were content in such cases to 

 resort to the magic of bioplasm as a sufficient explanation. 

 A description of the actual happenings in the definite terms 

 of chemical dynamics is his ultimate and perfectly reasonable 

 aim. To say merely that these sugars are " assimilable " and 

 therefore can be metabolised is to take an attitude towards the 

 operation of the bioplasm such as spectators take towards those 

 of the conjuror when he puts a golf-ball under a hat and later 

 displays a rabbit in its place. The physiological conversion of 

 one of the hexose sugars into another is comparatively easy 

 to understand now that it has been shown that dextrose, 

 fructose and mannose are mutually interconvertible in alkaline 

 aqueous solution. Starting with a solution of any one of them, 

 we find that after a time it contains all three in equilibrium. 

 By a process which ultimately involves an intramolecular 

 shifting of hydrogen atoms, though it is probably in essence 

 one of alternate hydration and dehydration, any one of these 

 sugars can assume an " enolic " or unsaturated form. This form 

 is the same in the case of all three sugars and from it all three 

 may be produced. The relationship will become clear when the 

 formulae of these carbohydrates are considered : 



The temperature and alkalinity of the body are not such as 

 would induce these changes with the required velocity and it 



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