CYTOPLASM 



20 1 



Stihmkroscopic morphology of selectively permeable membranes. A clear 

 picture of the permeability phenomena in the plasmalemma is ob- 

 tained with the aid of the permeability theory of K. H. Meyer (1955) 

 and T. Teorell (1955). This theory has been developed for mem- 

 branes with a framework structure and for this reason is also appli- 



Fig. 116. Morphological principle of K. H. Meyer's and T. Teorell's permeability theory 

 (1935). Molecular frame a) anionic, V) cationic, c) amphoteric. 



cable to the cytoplasm, which in our opinion is built on a similar 

 principle. The starting point of these ideas is that a molecular frame- 

 work represents a gigantic, polyvalent and immobile cation or anion. 

 In the case of the cytoplasm with its amphoteric character, the frame- 

 work can act either as cation or as anion, according as the p^ changes 

 (Fig. 116). 



One may imagine that, in the meshes of the framework, carboxyl 

 groups or amino groups, or both, are fixed as immobile members of 

 the main valency chains (Sollner, 1950). The first case may, for in- 

 stance, be realized in the pectin gel (Bonner, 1936a; Deuel, 1943) 

 of polyuronic acid chains (Fig. 116 a), when the framework acts as 

 an acid; the hydrogen ions are partly split off by dissociation and for 

 this reason cations can diffuse more easily through this molecular 

 structure than anions. Conversely, if the framework consists of basic 

 chains (e.g., of diamine acids, Fig. ii6b), the anion permeability 

 comes to the fore. Finally, the amphoteric cytoplasm (Fig. ii6c) is 

 more permeable to anions at low p^^ and to cations at higher pj^ values. 



These considerations apply not only to molecular frameworks, but 

 to the coarser meshworks of submicroscopic strands or globules as 

 well. This theory of the submicroscopic structure of the protoplasmic 

 surface and the cytoplasm may seem one-sided, in that it takes into 



