MITOCHONDRIAL STRUCTUKl'; AND Fl'NCTlON 



8s 



Fig. I. Section of beef heart muscle. X 28,700. 



laboratory to embark on a systematic program of degrading the mitochondrion 

 step by step and then reconstructing mitochondrial function and structure from 

 the composition and properties of the fragments. We can thus work on an ade- 

 quate scale to study chemically the components of the electron transport system 

 and of the mitochondrion. We have a little factory in our laboratory which pro- 

 duces each day about a liter of thick mitochondrial suspension from beef hearts, 

 and we can draw upon this supply, which is kept in the deep freeze, at our con- 

 venience. More and more biochemists have become aware of the virtues of heart 

 mitochondria, and others are now sharing with us the advantages of working 

 with such stable material. 



The electron microscope has been developed by Palade, Sjostrand, and others 

 into a very powerful tool for the study of mitochondrial structure. We have relied 

 heavily on this tool for insight into the nature of the processes by which we have 

 been able to fragment mitochondria into successively less complex fragments. In 

 this enterprise we have enjoyed the collaboration of Professor Hans Ris and, more 

 recently. Professor Paul Kaesberg and Mr. D. L. Filmer of the University of 

 Wisconsin. 



The first four figures^ show the transitional steps from intact heart mito- 

 chondria in situ to the least common denominator of oxidative phosphorylation, 

 the electron transport particles or ETP (34, 14). The mitochondrion in situ 

 (fig. i) shows a well defined outer envelope and an interior which is crammed 



^Electron micrographs (rtgs. 1-4) by D. L. Fihner anil F. Kaesberg, University of Wisconsin. 



