Passive diffusion of ions from an area of high to low concentration. 88

the unequal distribution of ions across the membrane; potassium more highly concentrated inside and sodium more concentrated outside. Sodium/potassium pump keeps sodium concentration higher outside.

A regular increase of decrease in the intensity or density of a chemical substance. Cells often maintain concentration gradients of H+ ions across their membranes. When a gradient exists, the ions or other chemical substances involved tend to move from where they are more concentrated to where they are less concentrated.

the difference in concentration between 2 compartment separated by the semi-permeable membrane.

A change in the number of molecules of a particular substance per unit volume between two points. The steeper the concentration gradient the greater the difference in concentration between the two points.

The difference in level of concentration between two areas. There is a tendency for molecules to flow, by chance movements, from regions of high concentrations to low concentrations.

The change in solute concentration per unit distance in solute. Concentration gradients cause Fickian diffusion (spreading) of solutes from regions of highest to regions of lowest concentrations. In slow-moving groundwater, this is the dominant mixing process.

A gradient within a given medium defined by the difference between the highest and lowest concentration of a solute. The solute will have a natural tendency to move from the areas of higher concentration to lower, thus diffusing.