MITOCHONDRIAL LIPIDS AND THEIR FUNCTIONS IN THE RESPIRATORY CHAIN 1 85 



Ubiquinone (Coenzyme Q) 



There is now a large amount of evidence which suggests that ubiquin- 

 one is a functional component of the respiratory chain. It is widely dis- 

 tributed in mitochondria, it undergoes enzymic oxidation-reduction and 



TABLE IV 



Concentration of Ubiquinone in Mitochondrial Preparai ions 



Preparation 



Ubiquinone 

 (^moles/g. protein) 



Pig heart-muscle preparation 4-0 



Horse heart-muscle preparation 40 



Guinea-pig kidney mitochondria i -6 



Rat liver mitochondria i 4 



Pig kidney mitochondria 1-2 



Arum viaciilatujii spadix mitochondria i -4 



it is able to restore enzvme acti\itv to soh ent-extracted preparations [14, 

 15- 16]. 



A survey of ubiquinone concentrations in a number of tissue prepara- 

 tions has been made by the method described bv Pumphrev and Redfearn 

 [1] and some results are shown in Table W . The concentration of 



TABLE V 

 Relative Concentrations of the Cytochromes and Ubiquinones 



Concentration 

 Preparation (/mioles g. protein) 



Ratic 



Ti UQ a b r ci UQ 



Pig heart- 

 muscle 

 prepara- 

 tion 0'74 o-b 00.S5 0-37 439 2-0 i-6 0-23 i -o 120 



Rat liver 

 mito- 

 chondria 0-13 0-13 0-I2 0-14 I'4I 0-93 0^93 0-9 I-O IQ-O 



The concentrations of cytnchnimes (/, b, and c were determined using the 

 wavelengths and molar extinction coefficients given by Chance and Williams [26] 

 and Ci from the data of Green et al. [27 J. 



ubiquinone relative to the cytochromes has also been determined in pig 

 heart-muscle preparations and rat li\er mitochondria (Table \). The 

 cytochrome concentrations were determined spectrophotometricallv after 

 solubilization of the preparations in sodium cholate. It will be seen that in 



