Ion Transport,Passive Diffusion,Primary Transport,Secondary Transport,Ionic Currents,Simport,Antiport,Molecular Mechanisms,Metabolic Reaction

Ion Transport

	Ion Transport Translocation of ions across biological membranes takes place by three different kinds of molecular mechanisms, passive diffusion, primary and secondary transport and ionic currents. Passive diffusion takes place through aqueous channels in the membrane, or through the lipid phase of the membrane. This type of movement is not common for ions
Transport is of two distinct types, primary and secondary ion transport. Primary ion transport (ion pump) involves movements linked to some enzyme reaction, e.g. Na+ and K+-stimulated ATPase of mammalian cells and proton translocation by vectorial redox reactions. Metabolic reactions provide the energy for moving ions against the electrochemical potential gradient. Primary ion transport involves Mitchell's chemiosmotic reactions which generate ion currents and also utilize them for chemosynthesis
Secondary transport involves exchange of secondary ionic bonds. In most cases secondary transport systems close the current loop. They couple the electrochemical potential of the ion gradient to perform other work. Ion movement may take place singly, or may be coupled to that or another metabolite. Ion movement may be in the same direction as the metabolite (symport) or in the opposite direction (antiport).
Secondary transport systems include (i) electrogenic symport of sugars and amino acids with one or more protons, (ii) electroneutral symport of non ionic metabolites and (iii) extrusion of sodium and calcium by antiport with protons

Index >> Membrane Transport >> Ion Transport

Ion Transport