CARBOHYDRATES 21 



with dilute mineral acids. They reduce metallic oxides in alkaline 

 solution, are optically active and extremely soluble. With phenyl- 

 hydrazine they form characteristic osazones. 



CH 2 OH 



I 

 GLUCOSE (CHOH) 4 



CHO 



Glucose, also called dextrose or grape sugar, is present in the blood 

 in small amount and also occurs in traces in normal urine. 1 After 

 the ingestion of large amounts of glucose, causing the assimilation 

 limit to be exceeded, an alimentary glycosuria 2 may arise. This 

 limit has been placed at 200-250 grams for normal individuals. 

 However, Taylor and Hulton 3 report five cases in which 500 grams 4 

 of glucose was fed and sugar appeared in the urine in only one in- 

 stance. In the case of starch and sucrose there also seems many 

 times to be no assimilation limit. In other words many normal indi- 

 viduals are able to assimilate as much of these carbohydrates as they 

 can eat and digest. When the sugar-handling mechanism is below 

 normal as little as 100 grams of glucose will cause hyperglycemia and 

 glycosuria. In diabetes mellitus very large amounts of glucose are 

 excreted in the urine. The following structural formula nas been sug- 

 gested by Victor Meyer for d-glucose: 



CHO 



H C OH 

 HO C H 

 H C OH 

 H C OH 



CH 2 OH 



(For further discussion of glucose see section on Hexoses, page 20.) 



EXPERIMENTS ON GLUCOSE 



The following tests are made on glucose as a typical carbohydrate 

 and are not specific for this sugar. A specific test for glucose is. the 



1 See Folin's test for sugar in normal urine (Jour. Biol. Chcm. t 22, 327, 1915): also. 

 Benedict: Jour. Biol. Chem., 31, 195, 1918. 



2 Benedict suggests the substitution of "glycuresis" for "glycosuria" (See pp. 414, 431) .. 



3 Taylor and Hulton: Jour. Biol. Chem., 25, 173, 1916. 



4 This was the maximum amount that the subjects of the tests could retain. 



