3 



O\3s3\>«3\3vJ\J\>0s2\3sJ\J 



Kinetic approach 

 to transport 



In the preceding chapter the reader may have observed how 

 many of the present conceptions of transport have flowed from 

 observations of the relationships of the rates of migration of a 

 substance to its concentration and to the concentration of analogs 

 and inhibitors. A brief consideration follows of the relationships to 

 be expected, assuming that transport occurs in some of the ways 

 considered in the last chapter. 



Diffusion 



We have already seen that the rate for net diffusion occurring 

 over a given area of membrane is given by 



V = * D (B, - S 2 ) (1) 



That is, the rate is governed by the nature of the membrane and 

 of the permeant as represented by the diffusion constant, and by the 

 concentration gradient. 



Chemical mediation 



If a mediation or facilitation of diffusion occurs whereby the 

 solute combines transiently with a mediating structure C to form 



45 



