Molecular/ionic species, movements

Nearly all biological processes involve the specialized functions of one or more protein molecules. Proteins function to produce other proteins, control all aspects of cellular metabolism, regulate the movement of various molecular and ionic species across membranes, convert and store cellular energy, and carry out many other activities. Essentially all of the information required to initiate, conduct, and regulate each of these functions must be contained in... 

The potential gradient that exists in the elextrolyte contributes negligibly to the movement of minor ionic species their transport is almost entirely by convection and diffusion. Therefore, the equations that are used for neutral species, such as for dissolved molecular oxygen, are also valid for minor ionic species. Convection refers to the macroscopic movement of a fluid under the influence of a mechanical force (forced convection) or of gravity force (free convection). At solid surfaces the velocity of fluids is zero and as a consequence only diffusion contributes to the flux at the electrode-electrolyte interface. This allows us to write the following expression for the flux of a minor ionic species B ... 

Insulator and capacitor applications depend on the dielectric properties of ceramics, that is, on their polarization response to an applied electric field. The four polarization mechanisms which describe the displacement of charged species in ceramics are (1) electronic polarization—the shift of the valence electron cloud with respect to the nucleus (2) ionic or atomic polarization— movement of cation and anion species (3) dipolar polarization—perturbation of the thermal motion of ionic or molecular dipoles and (4) interfacial polarization—inhibition of charge migration by a physical barrier. Further discussion of polarization phenomena may be found in Reference 1. 

Diffusion The movement of one atomic, ionic, or molecular species through another due to a concentration gradient or an electric field gradient. 

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