280 



ELECTRON TRANSPORT 



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 05 



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YOUNG CELL 



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 (KCN 



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Fig. 4. Effect of cyanide on oxygen consumption by light-grown 

 cells of/?, nibnim. Experimental conditions were the same as 

 for Fig. 1, except that potassium cyanide was added as indi- 

 cated. 



by half. Respiration of the cells heated at 55-60°C showed no response 

 on illumination, while the cells heated at higher temperature consumed 

 oxygen faster in light than in darkness. 



Chromatophores prepared from R. rw&rz/w according to the ordinary 

 method for the photophosphorylation assay and suspended in growth 

 medium consumed oxygen at rates comparable to those found for the 

 intact cells. At 24 °C the chromatophores showed oxygen uptake 

 stimulated by light, the rate in light being approximately twice as 

 fast as that in darkness. At 4° C the slowed oxygen uptake was inhibited 

 by light. The chromatophores. if heated at 95 °C for 5 minutes, coagu- 

 lated and still exibited oxygen uptake in light but none in darkness. 



