CHAPTER XVIIt. 



PROCESSES INFERRED FROM INDIRECT OBSERVATION; 



THE ENERGY-TRANSFORMATIONS IN 



LIVING ORGANISMS. 



THE INFLUENCE OF TEMPERATURE UPON LIFE-PROCESSES. 



The influence of elevation of temperature upon a chemical reaction 

 may be twofold. If the reaction is at all exo- or endothermic, that is, 

 if any heat is liberated or absorbed during the progress of the reaction, 

 an elevation of temperature will bring about a definite change in 

 Equilibrium so that at the conclusion of the reaction the final relative 

 proportion of the various components is altered. On the other hand 

 a rise in temperature always accelerates the attainment of equilibrium 

 whatever the station of equilibrium may chance to be. Thus, not- 

 withstanding the fact that the majority of the hydrolyses which occur 

 in living tissues are exothermic, so that a rise in temperature tends to 

 shift the equilibrium in the direction of less complete hydrolysis, yet 

 the rate of Hydrolysis being more than proportionately accelerated, 

 enzymatic hydrolyses which are barely perceptible at low tempera- 

 tures become extremely rapid at the body-temperature of warm- 

 blooded animals. 



The effect of temperature upon the velocity of a chemical reaction 

 may be expressed by the equation : 



, /Ti-To\ 



in which "ki," and "k " signify the velocity-constant at the absolute 

 temperatures "Ti" and "T " respectively, "e" is the base of the 

 Napierian logarithms and ^ is a constant, differing in different reactions, 



but almost invariably possessed of such a value that the ratio ^ 



ko 



exceeds 2 when TI T = 10. The Temperature-coefficient of a chemical 

 reaction therefore, or the ratio : 



Velocity of the reaction at T + 10 

 Velocity of the reaction at T 



is in almost every case greater than 2 and may be very greatly in 

 excess of this value. 



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