Cell Structure and Metabolic Regulation 31 

 Table IV 



Effect of added hexokinase on nucleotide levels in a medium 



in which mitochondria are undergoing oxidative 



phosphorylation 



Data taken from Siekevitz and Potter (1953). 



at these early points of increases we notice that the ATP in the 

 medium does not change in concentration. Either the hexo- 

 kinase which we add to the medium is not acting on the ATP 

 there, or, if it is, the adenosine diphosphate (ADP) resulting 

 goes into the mitochondria, is phosphorylated there to ATP, 

 and the ATP is secreted rapidly to maintain the ATP concen- 

 tration in the medium. Which is it? In Table V are the results 



Table V 



Effect of added hexokinase on concentrations and specific 

 radioactivities (sa) of intramitochondrial and extramitochondrial 



nucleotides and GLUCOSE-6-PHOSPHATE in a MITOCHONDRIAL 

 OXIDATIVE PHOSPHORYLATION SYSTEM 



Intramitochondrial 



Extramitochondrial 



Data taken from Siekevitz and Potter (1955). 



