46 



The Structure of Protoplasm 



TABLE 1 

 Generalized Protoplasmic Analysis 



Substance 



Water 



Proteins 



Fatty substances , 



Other organic molecules 

 Inorganic ions 



Percentage of 

 fresh weight 



85-90 

 7-10 

 1- 2 

 1- 1.5 

 1- 1.5 



TABLE 2 

 Relative Number of Molecules of the Various Types of Protoplasmic 



Materials 



These numerical proportions help us to grasp the cytoplasmic pic- 

 ture somewhat better since we may now think of one large protein 

 molecule surrounded by about 20,000 minute water molecules in 

 which the remaining relatively small molecules occur. 



To make this still more vivid, dimensions of these molecules and 

 their shapes are needed. These may be obtained by recourse to two 

 fields: to the chemical, which furnishes the structural formula and 

 the interrelationships of the atomic components; and to the physical, 

 which supplies the size and valence angles of the respective atoms. 

 From this information it is possible to determine the dimensions of 

 the molecules and also to obtain a great deal of information concern- 

 ing their spatial relations and other properties of their constituent 

 atomic groups (21) . Space limits us at this time to brief descriptive 

 notes of only the most prominent spatial characteristics of these 

 molecular structures. 



STRUCTURAL FEATURES OF COMPONENT MOLECULES 



Of the component molecules in protoplasm, water is the smallest 

 and apparently the simplest in structure. It has, however, charac- 



I 



