Osmosis

• Osmosis


  The diffusion of water molecules from an area of higher concentration to an area of lower concentration, through a selectively permeable membrane
• Osmosis is a passive process
• Selectively permeable membranes


  Allow some substances to pass through them, but not others
• In a dilute solution (higher water concentration than the cell contents)


  Water enters the plant cell by osmosis
• In a concentrated solution (lower water concentration than the cell contents)


  Water leaves the plant cell by osmosis
• Plasmolysis


  The process where the cytoplasm of a plant cell shrinks and pulls away from the cell wall when the cell loses water
• Red blood cells in a more dilute solution


  Gain water, swell and burst (haemolysis)
• Red blood cells in a more concentrated solution

  Lose water and shrink (become crenated or wrinkled)
• Osmoregulation


  Involving the kidneys to ensure the concentration of the blood stays about the same as the concentration of the cell contents