Control of Oxygen Utilization 



99 



[ADPJ>jM 



Fig. 5. The effect of ADP concentration upon the 

 extent of reduction of cytochrome a in the steady- 

 state. The increasing concentrations of ADP cause 

 increasing reduction of cytochrome a in the steady 

 state, as indicated by Fig. 4. Guinea-pig hver 

 mitochondria, succinate as substrate, 10° C. (Expt. 

 no. 382b) (From, Chance and Williams, 1956a. 

 Reproduced by permission of the Editors, J. biol. 

 Chem.) 



Phosphate addition 



800;jM E6.8mM 

 ADP 



6.8mMt:6.8mM 



Aerobic 

 Mitochondria 



"tris" buffer 



Fig. 6. Spectroscopic response of reduced pyridine nucleo- 

 tide to addition of phosphate. Mitochondria are suspended 

 in a phosphate-free medium and show no appreciable 

 spectroscopic response to ADP addition. Successive 

 additions of 6-8 mM phosphate causes oxidation of the 

 steady state level of the reduced pyridine nucleotide. 

 (Expt. no. 299b-19) 



