Mitochondrial Lipids and their 

 Functions in the Respiratory Chain 



E. R. Redfearn 



Department of BiocJiemistry, 

 The University of Liverpool, England 



Mitochondria contain relatively large amounts of lipids and there is 

 now a great deal of evidence which suggests that they play both structural 

 and functional roles in mitochondrial metabolism. We have been studying 

 the problem of lipid function in the respiratory enzyme system, both in 

 intact phosphorvlatmg mitochondria and in non-phosphorylating mito- 

 chondrial fragments. 



Nature of mitochondrial lipids 



Non-phosphorvlating preparations of pig-heart muscle [i] were 

 denatured with methanol and the lipid extracted with 40-60 light 

 petroleum. The extract was then chromatographed on silicic acid (Mallin- 

 krodt) and fractions eluted with increasing concentrations of diethyl 

 ether in 40-60 light petroleum. Stronglv adsorbing material at the top of 

 the column was eluted with methanol. One result of such an analysis is 



TABLK I 



Lipm Composition of Pio Heart-Miscle Preparation 



.... Concentration Percentage of 



ivipid , , . ^ , 1- ■ 1 



(mg./g. protein) total lipid 



Total lipid 



Phospholipid 

 Sterol 



Neutral lipid 

 Ubiquinone 



shown in Table I. The total lipid which amounts to 30",, of the total dry 

 weight of the preparation, contains 90",, phospholipid while smaller 

 amounts of sterol, neutral lipid and ubiquinone make up the total. 



All the fractions were examined spectrophotometricallv. Apart from 

 ubiquinone which showed intense selective absorption at 275 m^tt, a number 



