MITOCHONDRIAL STRUCTURE AND FUNCTION 



89 



/iT ^ 



.V* 











4% 



-1 



• •^*' yt/*^ • 



Fig. 6. Non-phosphorylating clcctrun transport particle. 



It should be pointed out that the electron transport particle is a submito- 

 chondrial unit of somewhat variable size which, however, is minute compared to 

 the dimensions of a mitochondrion. Each particle may well be an aggregate of 

 many repeating units. Only the fully disaggregated electron transport particle 

 would correspond to the individual repeating unit. Prolonged sonication of mito- 

 chondria does indeed lead to smaller and smaller particles which in the limit 

 could approach the dimensions of the repeating unit. But the chemical composi- 

 tion of the repeating unit as well as its enzymatic activity should be indistinguish- 

 able from any aggregate thereof such as the electron transport particle. The 

 particle or molecular weight of the repeating unit would be from 3.3 to 5 x lo" 

 based on the assumption of one molecule of DPNH dehydrogenase per repeating 

 unit. 



How the mitochondrion as a polymer is built up from the repeating units, the 

 nature of the structural principles which underlie the stacking of the cristae, the 

 exact relationship of the outer envelope to the cristae, and the role of the outer 

 envelope to the problem of }:)ermeability or accessibility, are fascinating problems, 

 but at present our information is too meager to do more than state them. 



It is highly significant that the isolated mitochondrion which is morpho- 



