324 



FINE-STRUCTURE OF PROTOPLASMIC DERIVATIVES 



III 



hydration water of the lattice and is partially mobile as swelling water. 

 The swelling maximum of the grains is governed by the linkage of 

 the chains. Adjacent layers have coalesced. The structure is wide- 

 meshed and porous, causing colourability and rodlet birefringence 

 (Speich, 1 941). In the process of pasting, the loosely linked, or 



Fig. 162. Possibilities of fine-structure in a layer of a starch grain (n = degree of poly- 

 meri2ation). a) Fine-structure of amy lose (n'-^2 5o); />) fine-structure of amylopectin 

 (n'-^8ooo); c) mixture of amylose {n^^z'^o) and amylopectin( n -^ 2,000,000); d) 

 amylopectin with inward pointing aldehyde group ; e) amylopectin with outward pointing 

 aldehyde group; /) amylopectin molecules with opposite orientation (from Frey- 



Wyssling, 1948 c). 



unlinked glucosan chains go into solution as amylose, whereas the 

 strongly linked amylopectin chains agglutinate throughout the paste. 

 Minor specific or individual variations in linkage may be responsible 

 for the peculiar resistance of different kinds of starch, or of different 

 grains within the same kind of starch. For instance, there are grains 

 of potato starch, the peripheral layer of which is so resistant to 

 ■enzymes that some of them may pass unaffected through the intestines 

 (Weichsel, 1936). 



To-day a more detailed discussion of the fine-structure in the starch 

 grain is possible, because the chemical constitution of amyloses and 

 amylopectins has been cleared up since 1938. Fig. 162 shows some 

 possible arrangements of these molecules with different degrees of 

 polymerization n in a layer i ^ thick of a starch grain (Frey-Wyssling, 

 1948c). The simplest case is represented by a), where only amylose 

 molecules with n--^ 250 (0.088 ix length) are drawn. However, since 

 the amyloses form only a minor portion of the starch grains (Table 



