CHAIRMAN'S INTRODUCTORY ADDRESS 



RATE-LIMITING FACTORS IN CELL 

 RESPIRATION 



Sir Hans Krebs 



Department oj Biochemistry, University of Oxford 



The origin of this symposium is a conversation between 

 Professor Martins, Professor Lynen and myself which took 

 place in Wiirzburg, in Professor Martins' laboratory, on 

 July 7th 1955. On July 6th I had given a lecture at Wiirzburg 

 on the "Steering of Metabolic Processes" (see Krebs, 1956, 

 1957) and on the day after my lecture Professor Lynen 

 happened to pass through Wiirzburg and stopped at Professor 

 Martins' Department for a few hours. We talked about the 

 regulation of metabolism and came to the conclusion that it 

 might be useful to have a Ciba Foundation symposium on this 

 subject, and thanks to Dr. Wolstenholme this symposium is 

 now taking place. I am indeed very grateful to him for 

 accepting the proposal and for organizing the conference. I 

 should like to make it clear that he carried the full burden of 

 the preparations. On matters of general policy Professor 

 Dickens gave much helpful advice. 



When biologists consider control mechanisms they usually 

 think of hormones and of the nervous system. Certainly these 

 play an important part in some of the mechanisms which 

 control metabolic processes. But control mechanisms also 

 occur in those forms of life which do not possess hormones or 

 nerve cells, such as the unicellular ones. For example, energy 

 may be obtained by fermentation if air is not available, or by 

 oxidation if air is present, the remarkable feature being the 

 controlled stoppage of fermentation by air. Among the most 

 striking regulatory mechanisms of lower organisms are those 



CELL METAB.— 1 1 



