CARBOHYDRATES 145 



Carbohydrates. Con. taste and dialyze easily. The 



solubility and sweetness as 

 well as power to dialyze 

 decrease as the number of car- 

 bon atoms increases. Those 

 with C 6 (or C 5 ) are called 

 monosaccharids; with 12, di- 

 saccharids or bioses; Cis, tri- 

 saccharids or trioses; Cj4, 

 tetrasaccharids or tetroses; 

 those with larger value of car- 

 bon are often termed poly- 

 saccharids. They usually have 

 the formula (C 6 HioO s )n. 

 Monosaccharids. Only the commoner forms 



will be mentioned. 



Arabinose Obtained by treatment of 



CsHioOs, (CH 2 (OH)-(CH- various gums with dilute 

 (OH) ) 3 - CHO) boiling H 2 SO 4 . 



d-Glucose (grape sugar, dex- This is the commonest sugar, 

 trose) It is in most cases the first car- 



C 6 Hi 2 6 , (CH 2 (OH)-(CH- bohydrate produced in pho- 

 (OH)) 4 -CHO) tosynthesis. It occurs abun- 



dantly in most sweet fruits. 

 It is the form in which carbo- 

 hydrates are translocated. 



d-Galactose (formula as for glu- Produced by the splitting of 



cose) the lactose, raffinose, or man- 



neotetrose molecule by weak 



acids, therefore one of the 



constituents of these sugars. 



d-Mannose (formula as for glu- Produced by the splitting of 

 cose) the molecule of certain (re- 



serve) celluloses by weak acids 

 and therefore one of the con- 

 stituents of those carbohy- 

 drates. 



d-Fructose (fruit sugar or levu- This sugar is abundant in 

 lose) many sweet fruits, e.g. grape. 



C 6 H 12 6 , (CH,(OH)-(CH- 

 (OH)) 3 -CO-CH 2 (OH)) 

 10 



