62 



The Structure of Protoplasm 



give us a somewhat broader view of the molecular constituents 

 of the particles in cytoplasm. Of the dozen or more prosthetic 

 groups, each has its own specific protein molecule, at least in vitro, 





,^♦ 



Fig. 10. A. Adenosine triphosphate, a nucleotide plus two phosphoric acid 

 groups. B. Flavine-adenine dinucleotide. C. Nucleic acid, a tetranucleotide. 



to which it may be attached. If we think of the attachment as being 

 associated with the patterns or mosaics formed by end groups of 

 particular amino acid residues on the surface of the protein particle, 

 then a specific protein may mean that in order to fit a prosthetic 

 group of one sort the configuration of the chain is different than 

 when it fits another prosthetic group. In other words it may not 

 mean that the amino acid composition of the chain is necessarily 

 different in order to have specific properties but that merely a 

 difference in configuration or arrangement of the chain lengths in 

 the particle would suffice, since this would alter the patterns formed 

 by the residue end groups. 



With these conceptions of the spatial and electrical properties of 

 the various constituents of cytoplasmic particles, we see the need 

 for restrictions or limitations on the infinite number of ways in 

 which these materials could aggregate to form cytoplasmic particles; 

 without these a future comprehension of the larger structures seems 

 practically impossible. This aggregation, it has been pointed out 

 (99) , may be brought about by means of three sorts of bonding 

 forces: primary valence bonds, such as cystine bridges; bonds due 

 to electrostatic forces, such as charged groups, or ions; electrostatic 

 effects as observed in hydrogen bridges; and van der Waals' 



4 



