Osmosis

Topic Description

Osmosis is any movement of water across a selectively permeable membrane. The concentration of solutes within the cell’s cytoplasm compared to the concentration of solutes in the extracellular fluid surrounding the cell, will cause water movement either into or out of a cell. When a cell is surrounded by an isotonic solution, this means the solution around the cell has an equal concentration of solutes when compared to the concentration of solutes within the cell’s cytoplasm. Therefore, water will move into and out of the cell equally, and thus no net gain or loss of water. When a cell is placed in an isotonic solution, the cell will ultimately maintain its size. When a cell is surrounded by a hypertonic solution, the solution around the cell has a higher concentration of solutes when compared to the concentration of solutes within the cell. Remember, the high concentration of solutes outside the cell will have a concentration gradient moving into the cell due to the differences of solute concentration. This of course means that the solvent, water, will have its concentration gradient moving The opposite way direction, moving out of the cell toward the higher or hyper concentration of solutes outside of the cell. When a cell is surrounded by a hypotonic solution, the solution around the cell has a lower concentration of solutes when compared to the concentration of solutes within the cell. In the case of a hypotonic solution, due to solute concentration differences, the resulting osmosis that occurs results in water entering the cell more rapidly Than it exits.