PERMEABILITY AND IMPERMEABILITY OF CELL MEMBRANES FOR IONS
This extract was created in the absence of an abstract.
Excerpt
Ion Permeability
The ion permeability of the plasma membrane has long been recognized as an important problem in cell function. A considerable portion of present day blood chemistry, for example, depends upon a membrane permeability to ions. On the other hand, many osmotic measurements of the membrane permeability to water and molecular solutes have been interpreted on the assumption of a negligible ion permeability.
A permeability may be defined phenomenologically as the amount of substance transported across a unit area in unit time as the result of a unit force. The most convenient and widely used driving force is that of a concentration gradient which applies to both molecules and ions. It is quite obvious that a more direct measurement of the ion permeability might be expected from the application of a gradient of electrical potential which will tend to move only the ions—and when the ions move, they constitute...
