92 



Britton Chance 



rate obtained following its expenditure (Chance and M. 

 BaltschefPsky, 1958). Loosely coupled mitochondria are much 

 more easily detected by this criterion (see Fig. 2). Because 

 the affinity of the mitochondria for ADP is so much higher 

 than for phosphate (see below) and respiration therefore so 

 much more easily started and stopped by small additions of 



Vibrc,,ng^pla,inun, ,,,„,„, 

 Glass electrode 



Fig. 1. Polarographic method for measuring oxygen utiliza- 

 tion of mitochondrial suspensions employing a vibrating 

 platinum microelectrode and a calomel reference cell con- 

 nected to a salt bridge. The electrode is vibrated at 60 c.p.s. 

 by the reed of a "Brown Converter." The electrical circuit 

 converts the electrode current to an alternating voltage. 

 (Expt. no. MD 33b) 



ADP, we have, as a practical consideration, not used phos- 

 phate for a determination of respiratory control ratios. 



Respiratory control ratios can be satisfactorily measured 

 in the Warburg respirometer, as indicated by the work of 

 Lardy and Wellman (1952). It has, however, been found more 

 convenient to use polarographic methods employing either a 

 stationary platinum electrode (Davies and Brink, 1942) with 

 a rotating cup (G. R. Williams, unpublished) or a vibrating 

 platinum microelectrode (Chance and Williams, 1955a). Of 

 the two methods, the latter has a much more rapid response. 

 An illustration of the arrangement of the platinum micro- 



