II. MOLECULAR MORPHOLOGY 

 AND GROWTH 



BY FRANCIS O. SCHMITT^ 



MOLECULAR morphology and growth are both very large subjects. 

 Their combination encompasses a respectable portion of the 

 content of biology. If we are to bring into sharp focus a few of 

 the fundamental problems, to achieve a measure of synthesis and projec- 

 tion into profitable paths of future investigation, certain limitations of 

 scope must be imposed. 



One of the uniquely characteristic properties of protoplasmic systems 

 is the structural organization by which the various energy-giving re- 

 actions are coupled and coordinated with the molecular effectors, the 

 "machinery," of the cell. While the molecular morphology of the com- 

 ponents which participate in cellular energetics, the enzymes, hormones, 

 metabolites and so on is also highly critical, we shall concern ourselves 

 chiefly with the macromolecular constituents of cell structure and in 

 particular with the fibrous proteins. 



In discussing a subject as broad as that of growth, it would be im- 

 possible to exclude so important a subject as the globular proteins, since 

 many of the enzymes which preside over cellular energetics belong in 

 this category. As we shall see, a consideration of fibrous proteins in- 

 volves the globular proteins very closely. Unfortunately the space 

 allotted here is too limited to permit a full discussion of the detailed 

 structure of proteins generally. 



I am not unmindful of the importance, for cell structure, of protein 

 complexes which are not perceptibly fibrous in nature. Included with 

 these are the various cytoplasmic particulates such as the microsomes, 

 secretion granules, Nissl substance and so on. However, polarization 

 and electron optical evidence indicates that the fibrous proteins form the 

 basis of the molecular fabrics which constitute the structural matrix of 

 the cell. Hence my own remarks will be limited to this aspect of molecu- 

 lar morphology. 



With these apologies I shall proceed with a brief statement of the 

 present state of knowledge about the fibrous proteins and offer some 

 suggestions about fruitful fields for further study. 



1 Department of Biology, Massachusetts Institute of Technology, Cambridge, Massa- 

 chusetts. 



