MITOCHONDRIAL LIPIDS AND THEIR FUNCTIONS IN THE RESPIRATORY CHAIN 1 89 



spectrophotometric examination of light petroleum extracts of mito- 

 chondria did not reveal anything with the spectral characteristics of 

 uhiqiiinol monophosphate. 



Summary 



1. Mitochondrial preparations contain relatixelv large amounts of 

 phospholipids with smaller concentrations of neutral lipid, sterol and 

 ubiquinone. 



2. The extraction of mitochondrial preparations with organic solvents 

 was studied and three principal effects were distinguished. 



3. The concentrations of ubiquinone in a number of mitochondrial 

 preparations were measured. Ubiquinone concentrations with respect to 

 the individual cytochromes were shown to be relatively high. 



4. The steadv-state oxidation-reduction levels of ubiquinone in rat- 

 liver mitochondria in various metabolic states have been measured. The 

 possible role of ubicjuinone in oxidative phosphorlvation was discussed. 



Acknowledgment 



The author is indebted to Dr. Alison AI. Pumphrey and Mr. G. H. 

 Fynn for their collaboration in this work. 



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