18 GENERAL CONCEPTS 



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Figure 2.2. An electron micrograph of a section of a cell from the pancreas of a 

 guinea pig. A segment of the nucleus (n) surrounded by its nuclear membrane, some 

 mitochondria (m), which are sausage-shaped structures with double-layered transverse 

 partitions, and the paired, spaghetti-like strands of the endoplasmic reticulum or mi- 

 crosomes are evident. (Courtesy of G. Palade.) (Maximow and Bloom: Textbook of 

 Histology.) 



microscope, they are found to have the same structure exhibited by 

 comparable structures in the intact cell. The separated particles can 

 then be suspended in suitable incubation media and their metabolism 

 can be studied. Such separated mitochondria and microsomes will carry 

 out many biochemical reactions, and much is now known about the 

 functions of each of these particles. The liquid left after the homogenate 

 has been subjected to high centrifugal force to sediment the microsomes 

 contains many other enzymes which apparently exist in the cell more or 

 less free in the ground substance of the protoplasm. 



