Biological interphases models

Against simplistic views of the FIAM, it is necessary to stress that the model does not imply that the free metal ion is the only species available to the microorganism [2,14], Indeed, the internalisation flux (i.e. the rate of acquisition) depends on the free metal ion concentration at the biological interphase (which in the FIAM is practically cj ), but metal bound to a ligand in the solution can dissociate, can diffuse (under a negligible gradient according to the FIAM), and can eventually be taken up. 

Q.19.3 Is tire Stern or Grahame model of the interphase to be preferred over the Gouy - Chapman or Helmholtz model in biological systems ... 

A. 19.3 While the best model depends on the question being investigated, the Stern model would provide a more accurate model of the interphase because it considers molecular size and non-electrostatic molecular absorption, both of which are very important to biological systems. For example, proteins control the flow of ions through membranes based on size, so if size isn t considered, the interactions leading to flow control would be missing an essential component. Hydrophobic and hydrophilic interactions are also an important part of interphase interactions. 

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