GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

11. FUNDAMENTAL MECHANISMS OF METABOLISM AND ENERGY CONVERSION IN MICROORGANISMS

11.7. MECHANISMS OF SUBSTRATE UPTAKE

11.7.1. Passive diffusion

The transported substance does not interact specifically with the components of The Cell membrane. It passes through the membrane until equilibrium is established between the intracellular and extracellular concentrations. Since in nature the concentration of most metabolites inside the cell is higher than outside, it is evident that transport via passive diffusion is not very widespread and is limited to a small group of substances, namely gases (oxygen), Water, and certain ions. Inhibitors, toxins, and other foreign substances not typical of the cell also penetrate it via simple diffusion. In E. coli, sodium ions enter the cell by passive diffusion, whereas potassium and magnesium ions are actively transported. However, other Bacteria utilize active sodium transport systems.



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