Isoosmosis

As iso-osmotic refers to two solutions having the same number of dissolved particles contain (analog: hyperosmotic and hypoosmotic ).

An iso-osmotic solution does not have to be isotonic at the same time , since cell membranes can have different permeability for particles, which can cause considerable osmotic pressure . The osmolarity , on the other hand, does not depend on the permeability of the cell membrane for dissolved substances.

An isotonic saline solution has an osmotic value of approximately 300 mosmol and is iso-osmotic at the same time. If a cell is in such a solution, the pressure on both sides of the cell membrane is the same. In contrast, a 300 mosmol urea solution is iso-osmotic, but not isotonic: the cell membrane is well permeable to urea molecules, so the dissolved urea has no effect on the osmotic pressure. Water penetrates the cell through osmosis and increases the pressure inside, which in animal cells that are not protected by a cell wall can cause the cell membrane to tear.