ENERGY SUPPLY OF THE CELL 65 



molecule. The catalyst in either case must be an 

 unsaturated compound. If the hydrogen would com- 

 bine with the catalyst permanently, it would lose its 

 power as activator. A third compound steps in to 

 prevent this, namely the hydrogen acceptor which com- 

 bines with the loosened, activated hydrogen atoms thus 

 becoming itself reduced while oxidizing the hydrogen 

 donator. The hydrogen acceptor may have to be 

 activated as well. We are certain of this in the process 

 of respiration where oxygen is the final hydrogen acceptor, 

 and will act only if activated by some complex organic 

 iron compound. 



The gradual breaking up of the carbohydrate through 

 a number of intermediate steps leads to the question 

 whether for each of these steps, a separate enzyme is 

 necessary. It would seem that what we had called 

 zymase (p. 36) must be a large group of individual 

 enzymes. In fact, several of them have already received 

 names, such as catalase, reductase, alcohol oxidase, 

 lactozymase, lactacidase, carboxylase, carboligase, 

 methylglyoxalase, mutase, dismutase, etc. 



We have no criterion for the purity of an enzyme 

 and therefore might always assume that a supposedly 

 pure enzjone contains another enzyme if it gives a new 

 reaction under changed conditions. However, the num- 

 ber of different enzymes in one bacterial cell would 

 have to be so large under the circumstances that it 

 seems rather impossible to concentrate so many molecules 

 of the size of enzyme molecules in such a small space. 

 (The dimensions of bacteria will be discussed on p. 397.) 



Kluyver and Donker (1926) have endeavored to show 

 that Wieland's theory of hydrogen activation, as the 

 underlying cause of all oxido-reduction, brings a unifying 

 principle into biochemistry. It does not seem necessary 



