Biology - Osmosis

Osmosis is the movement of water from a high water concentration to a low water concentration through a partially permeable membrane. Osmosis takes place in all living cells.

If a red blood cell is placed in water, water enters the cell by osmosis. As the volume, and therefore pressure, in the cell increases it will burst. This is because the membrane is quite weak. When red blood cells are places in a concentrated sugar solution they appear wrinkled when viewed through a microscope because the water moves out of them by osmosis.

This does not happen inside the body because the kidneys make sure the concentration of the blood stays about the same as the concentration of the solution inside the red blood cell.

• Lysis – bursting an animal cell by osmosis
• Crenation – shrinking an animal cell by osmosis