Osmosis

• Osmosis can be defined as the spontaneous movement of water molecules from an area of high concentration, to an area of lower concentration through a partially permeable membrane.

• Osmosis refers to the movement of water molecules only.

• The concentrated solution has low concentration of water molecules.

• A dilute solution has high concentration of water molecules.

• Osmosis can happen in either direction, that means water can move in either direction depending on the relative concentration of dissolved substance.

• Water will diffuse from a high water potential to a low water potential.

Osmosis in living cell

• The cell membrane of animal is partially permeable.

• Animal cells, which do not have cell walls, can respond adversely to change in the surrounding water pressure.

• In pure water, the plant cells take up water by osmosis and become turgid.

• In a more concentrated solution, the cell contents lose water by osmosis, and become flaccid.

• Cells have dilute solutions of sugars, amino acids and mineral ions.

• Animal cells also take in and lose water by osmosis. Animal cells do not have a cell wall, therefore they change size and shape when put into solutions of different concentration.

• In animals, the concentration of body fluids must be kept within optimal limits. Cells will not function efficiently if they lose or gain too much water by osmosis.