Osmotic Pressure

Definition

Water diffuses through semipermeable membranesfrom low- to high-solute- concentration solutions. This process is known as osmosis. Osmotic pressure is the pressure produced on the semipermeable membrane of an organism by the difference in solute concentration between the internal and the external part of the cell. When the solute concentration in the interior of the cell is as that of the medium, we say that the solution is isotonic, no diffusion takes place. Normally, cell systems develop in environments where the solute concentration is lower than the cytoplasmic solute concentration. In this case, water diffuses from the medium to the cytoplasm. Halophilic organisms grow in solutions where the solute concentration is much higher than the cytoplasmic one. In this case, there is a tendency for water to flow out of the cell to diminish the osmotic pressure on the membrane. This can produce severe problems for cells if they have no means with which to deal with it....