Appendix 1: 



Terminological 



considerations 



The term transport 



With the present enormously increased biological interest in 

 transport we see this term occasionally used very broadly. Without 

 any desire to set arbitrary limits to the biological area interesting to 

 those who work in this field, I urge that we continue to define 

 transport as the process by which a solute is transferred from one 

 phase to another, being in the same initial and final states in the 

 two phases. Let me set up a series of hypothetical examples of the 

 uptake of solutes by tissues or cells, to see how this definition 

 operates: 



Case 1. Cupric ion is fixed by liver slices, whether at 37 or 100°, 

 by complexing with accessible groups. Dissociation from super- 

 ficial sites, followed by more stable association with deeper ones, 

 will be involved. 



Case 2. A solute supplied exogenously does not mix with its sup- 

 posed endogenous equivalent, because the endogenous equivalent is 

 actually a different chemical species. A genetic variant permits 

 mixing, because it has the capacity to convert the solute to the 

 form present endogenously. 



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