Molecular Structure in Protoplasvi 



63 



cohesion forces. The most important of these are the electrical 

 effects arising from the existence of ionized groups, since they may 

 act at considerable distances as well as at close range, while the 





9 



r A> 



Fig. 11. A. Portion of the prosthetic group of Cytochrome c. B. Chlorophyll 

 A. The large central ball in the porphyrin ring represents iron in Cytochrome 

 and magnesium in Chlorophyll. 



other types are effective mainly at short distances, a matter of 1 to 

 about 5 Angstroms. 



Here, again, we come to the borderline between the physical- 

 chemical and the biological viewpoints. Aggregates formed by all 

 possible combinations of these various molecules would produce 

 merely a heterogeneous mixture in the cell, while opposed to this, 

 organization is characteristic of the living protoplasm. Nevertheless, 

 the various means of attachment, no matter how they are brought 

 about, are undoubtedly the same in living as in inert matter; and 



Fig. 12. A. Thiamine pyrophosphate (97, 98). B. Glutathione, glutamyl- 

 cysteinylglycine (88). The very lightly-colored ball near the middle in each 

 model represents a sulfur atom. 



while it seems probable that the discrete molecules and particles, 

 such as we have selected from the proteins, fats and other organic 

 molecules, may not take exactly the same relative arrangement in 

 space in vivo as they do in vitro, comprehension in the latter seems 

 likely to aid in an understanding in the former. 



To this end a few points concerning the attachment of various 

 combinations of molecules is introduced. We need not dwell on the 



