ENERGY SUPPLY OF THE CELL 119 



In solutions containing more than 1 % of sugar, the rate 

 of alcohoHc and of lactic fermentation is practically 

 independent of the sugar concentration. The rate of 

 oxidation of ammonia by Nitrosomonas is also constant 

 if the oxygen pressure is more than one-half of that of the 

 atmosphere, and the rate of nitrite oxidation by Nitro- 

 bacter is constant above 0.1% nitrite. 



(/) INFLUENCE OF TEMPERATURE ON THE RATE OF 

 FERMENTATION 



1. INFLUENCE OF TEMPERATURE UPON CHEMICAL 

 PROCESSES 



Those chemical processes of which the rate is measura- 

 bly slow, are accelerated by an increase in temperature. 

 The rate of the processes is increased, and the rate of 

 increase is called the temperature coefficient, usually 

 designated by the letter Q. It is obtained by dividing 

 the rates of reaction measured at different temperatures, 

 Ki&t T, andjK:2 at T -{-AT: 



O - — ' 



For most chemical processes, at temperatures of biological activity, 

 this coefficient for 10°C. increase, Qio, lies between 2 and 3. 

 van t'Hoff formulated this temperature relation 



where Ti and T^o are absolute temperatures (degrees Centigrade 

 +273). This shows that the temperature coefficient is an expo- 

 nential function, and this must be taken into consideration when 

 Qio is computed from any temperature intervals other than 10°C. 



The following reasoning will demonstrate the principle: Assumed 

 that the rate of a process is increased by the coefficient Qi for 1°C. 

 increase. 



