CHAPTER 8 



Speeds of Some Processes in 

 Biological Systems 



The ultimate goal of biophysical kinetics is the understanding of that 

 remarkable integration of heat, mass, and work transfer by chemicals which 

 maintains so reliably the steady-state condition in every spot in the living 

 system. 



INTRODUCTION 



Biophysical kinetics is the study of the rate or speed at which chemical 

 reactions or physical processes take place. Factors which influence the speed 

 are elucidated in detail, when possible, by experimental methods, and are 

 then analyzed in terms of the actions of the molecules which give the over- 

 all result. It is the study of mechanism of reaction, and of molecular mech- 

 anism in particular. 



Kinetics is formally defined as "that branch of dynamics which treats 

 changes in motion produced by forces." It is the purpose of the subject to 

 define and interpret these forces, which may be functions of temperature, 

 pressure, molecular interactions, concentration gradients, electrical poten- 

 tial, etc. 



Within the broad field of kinetics there are two main subjects which are of 

 interest in biology: 



( 1 ) Kinetics of chemical reactions in solution. 



(2) Kinetics of physical process such as diffusion, fluid flow, transport of 

 electrical charge, and heat conduction. 



The basic principles of the main subject are sketched, and then each 

 of the subjects of particular interest is considered. Since chemical re- 



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