198 



C. Martius 



a phosphorylating one and a non-phosphorylating one, are 

 provided in the cell, this fact must have physiological signifi- 

 cance. Apparently, the cell is prepared for the oxidation of 

 hydrogen without coupled phosphorylation, at least in the 

 first two steps of the respiratory chain. The problem now 

 arises of how the electrons or hydrogen atoms are directed in 

 one or the other direction. In normal, intact mitochondria, 

 they seem to take exclusively the pathway which is coupled 



DPNH 



T1»NH 



Diaphorase Cytochrome c reductase Vitamin K reductase 



Vitamin K 



-Cytochrome h 



Cytochrome q 



i 

 Cytochrome c 



Cytochrome a + ag 



Oxygen 



Fig. 1. 



with phosphorylation and leads via vitamin K reductase, 

 vitamin K and cytochrome h (Fig. 1). This pathway, however, 

 appears to be very sensitive to any alteration of the internal 

 structure of the mitochondria, probably because some of its 

 constituents are structurally firmly bound. If their combina- 

 tion is disturbed, the electrons, as in the case of the gap pro- 

 duced by vitamin K deficiency, have to take the emergency 

 exit, as it were, via cytochrome c reductase to cytochrome c. 

 The same seems to hold true if, instead of internal formation of 

 DPNH, DPNH is added from outside to the mitochondria. 

 In this case, as Cooper and Lehninger (1956a) have demon- 



