lo8 PLANT RESPIRATION 



The simultaneous oxidation of autoxidators and acceptors 

 by molecular oxygen from the atmosphere is a very clear exam- 

 ple of coupled reactions. If we represent the autoxidator by 

 A and the acceptor by B, the general nature of the coupled 

 oxidation may be represented as follows: 



(I) A + Oo - AO2 



(II) AO2 + B = AO + BO. 



This is a simple case of chemical induction. The reaction of 

 the oxidation of B by atmospheric oxygen, which cannot take 

 place of itself, is set in action by the simultaneous oxidation of 

 A. Sometimes all the oxygen passes over to B as follows: 



(I) A + O2 = AOo 



(II) AOo + B = AO + BO 



(III) AO + B = A + BO. 



It is evident that only the specific reaction velocities of the 

 single stages determine whether the whole process exhibits 

 chemical induction or catalysis. That is to say, if the velocity 

 of reaction II is greater than that of reaction III, AO as well 

 as BO is formed by the process as a whole. If the ratio of the 

 reaction velocities is reversed only BO is formed as the end 

 product of the oxidation, since in this case the total process is 

 expressed by the equation: 



A + 2B + O2 = A + 2BO. 



This is a typical case of the so-called "catalysis by means of 

 intermediate products." It is evident that this kind of cataly- 

 sis is nothing but a special case of chemical induction. 



It must be made clear that, to all appearances, oxidation 

 catalyses appear in living cells but very seldom or not at all. 

 A chemical induction consisting of a greater number of stages 

 often takes place in the living protoplasm. Very often the 

 activation of oxygen effected by the formation of moloxide 

 proves to be insufficient. A further increase in the oxidation 

 potential is necessary for the oxidation of certain acceptors. 

 This raising of the potential^ is evoked, among other ways, by 

 means of the formation of secondary peroxides. Typical cases 



' It is practically immaterial whether we have to do here with a real increase in potential 

 or with a reduction of the passive resistance. The; latter supposition is theoretically more 

 probable. 



