268 



X-ray Analyses of Proteins and Nucleic Acids /1 5 : I 



Figure 1, illustrating the features of many different types of cells. The 

 structures shown in Figure 1 are based on the results obtained with a 

 variety of techniques. In the figure, there are two major subdivisions : 

 the nucleus and its contents, often called nucleoplasm ; and the remainder 

 of the cell, sometimes called cytoplasm. Both the nucleus and the cyto- 

 plasm are surrounded by .membranes, as are also the smaller formed 



Crystallites 



Starch or 



Glycogen 



Granuoles 



Chromatin 

 Substance 



Nucleoplasm /^ 



Mitochondria 



Membrane 



Magnified Section through 

 a Mitochondrion 



Cytoplasm 



Endoplasmic Reticulum 



Ribosome t 

 (may be artefact) 



Granum 

 Membrane 



Secretion* 

 Granuoles 



Cell Wall 



Centrioles 

 {See Chapter 

 Mitosis) 



Fibrils 

 (See Chapter 8) 



10- 



Cell or 



Plasma 



Membrane 



Magnified 

 Chloroplast 



^Protein 





Magnified 

 Membrane 



Phospholipids 

 Protein 



* = Non-living, not present in all cells, does not contain protein 

 (g> = Not present in all cells 



Figure I. Composite cell. Plasma membrane, nuclear mem- 

 brane, chloroplast membrane, and mitochondrial membrane 

 all probably have the form shown for the membrane on the 

 right. All elements except those marked with * contain 

 proteins, whereas nucleic acids are found only in elements 

 marked %• The endothelial reticulum is believed to extend 

 throughout the cytoplasm, possibly dividing it into vesicles or 

 compartments. After A. W. Ham, Histology (Philadelphia: 

 J. B. Lippincott Company, 1957). 



elements such as the mitochondria and the Golgi bodies. These membranes 

 consist partly of proteins and partly of other compounds called lipids 

 (for example, fatlike compounds). The membranes not only give 



