ENZYME-SUBSTRATE COMPOUNDS 



that occurs when oxygen is suddenly added to the reduced com- 

 ponents of the respiratory chain, it is easy to see by inspection 

 that the time sequence of the oxidation reactions will be the chem- 

 ical sequence for the abbreviated system: 



O2 + az" — ^ az'" + O2- (13) 



m'" + a" -^^^ a^" ^ a'" (14) 



a'" + c" — ^ a" + c'" (15) 



The differential equations are 



daJ" 



dt 



da'" 



= kiiO^W - kiat"'a" (16) 



= kzai"'a" - Ka"'c" (17) 



dt 

 Near t = 0, as'" and a'" are negligible and 



^^»^^' (18) 



dt ^ dt ^ ' 



In fact, the ratio of these initial reaction rates can approach a 

 value dependent on the ratio [02]/<2'". 



For this simple example the terminal component of the 

 respiratory chain is identified, and, by following the time se- 

 quence, the chemical sequence of the other components can also 

 be determined. By adding an electron donor to the oxidized 

 system the reaction sequence in the opposite direction can also be 

 determined. A third alternative is to add suddenly a terminal 

 inhibitor such as azide or cyanide and observe the sequence of 

 reduction of the components. 



ANALOGUE COMPUTER 



The evaluation of the time separation that may be expected 

 from a sequence containing components of different concen- 

 trations and reaction velocity constants can best be determined 

 by means of an electronic analogue computer. In this case it is 

 unnecessary to neglect the concentrations a^ ' and a ' as above. 



325 



