STARCH 



159 



in which the basic molecule is enclosed in a round bracket, 

 while the degree of polymerization is indicated by the square 

 brackets. 



According to Pringsheim,* the a and j3 series of dextrins 

 are derived from amylose and amylopectin respectively, and 

 diamylose and triamylose he regards as the basal nuclei of 

 amylose and amylopectin to which substances he assigns 

 the following structure :— 



— CH o CH 



(CHOH). 



L 



O CH 



-0 



CHOH 



I 

 -CH 



O 



Choh 



— CH., 



(CHOH)^ 



I 

 -CH 



Amylose [(C6Hi„05)2]„ 

 O- 



-CH 



(CHOH), 



O CH O 



i 

 CHOH 



-CH, 



O CH,--CHOH— CH— (CHOH). 



-CH . (CHOH),- 



-CH 



I 

 O 



1h- 



-CHOH— CHo 



O 



Amylopectin [(CgHio05)3],, 



Moreover, the fact that by the action of cold concentrated 

 acid upon glycogen, he has also obtained triamylose leads 

 him to believe that the amylopectin of starch is identical with 

 glycogen. 



In Ling and Nanji's f opinion, however, the basal unit 

 of the polymerized amylose and amylopectin of the starch 

 granule are a-hexa-amylose and a^-hexa-amylose respectively 

 (for formulae, see p. 157). 



Reactions. 



I. The appearance of the grains under the microscope 

 and their action on polarized light in the presence of water 

 are well known. 



* Pringsheim : " Ber. deut. chem. Gesells.," 1924, 57, 1581. 

 t Ling and Nanji : "J. Chem. Soc," 1923, 123, 2683. 



