SELECTED PAPERS 



utilization of the dissimilation that accompanies the reconstitution of 

 yeast in an advanced state of autolysis by the sudden addition of sugar 

 is quite considerable. On this basis one would again be inclined to 

 conclude that the formation of cell constituents represents a process 

 that occurs with a very low energy efficiency, in other words, that the 

 energy derived from some chemical transformation can co-operate 

 in a second reaction only if concomitantly a considerable part of the 

 energy is dissipated as heat. 



If now we try to formulate this problem more succinctly, it must be 

 stated that the metabolism of a living cell, which presumably pro- 

 ceeds isothermically, shows us a reaction that leads to an increase in 

 free energy, viz., the assimilation, which obviously is conceivable only 

 if concomitantly a second reaction occurs which proceeds with a 

 larger loss of free energy, so that the free energy of the entire system 

 decreases considerably. Hence I should like to ask the physical chem- 

 ists amongst my audience whether they know of similar cases of cou- 

 pled reactions in inanimate systems, and in how far they would have 

 fundamental objections to accepting the occurrence of such energetic 

 coupling. 



Euler and Af Ugglas [191 1] have posed this question as early as 

 191 1, though perhaps in a less pregnant form. They believe that such 

 energetic interplay between two materially independent reactions is 

 conceivable if both reactions are accelerated by one and the same 

 catalyst. They elucidate this by referring to displacements in equilib- 

 ria that must neccessarily happen if the catalyst forms compounds 

 with the two substrates as well as with the reaction products. Without 

 here entering into a detailed evaluation, it follows from the necessity 

 to assume a coupling of dissimilation and assimilation that it is entirely 

 inconceivable that the energy-yielding dissimilatory process would 

 occur under the influence of a catalyst that can be divorced from the 

 remainder of the living cell. Such a concept, advocated rather thought- 

 lessly by chemists after Buchner's discovery of zymase, can only be 

 defended by those who are blind to the biological significance offer- 

 mentation as the dissimilatory process of the yeast, and which conse- 

 quently has to be considered in connexion with the assimilation. 



That the dissimilatory reactions, in contrast to the preparatory 

 conversions of foodstuffs, occupy a special position in the cell is clearly 

 reflected by the fact that the latter occur under the influence of en- 



