Diffusion and Osmosis

Diffusion

• Diffusion is a process whereby a substance moves from its region of high concentration to its region of low concentration.
• The process is a passive transport which does not require energy to take place.

Diffusion in living organisms

• Organs have specialized features to increase the surface area for diffusion of materials.

Osmosis

• Osmosis is a process whereby water molecules move from the region of high water concentration (high water potential) to the region of low water concentration (low water potential) through a partially (or semi- or selectively) permeable membrane.
• Partially permeable membrane is a membrane that only allows certain substances to pass through.
• All cell membranes of living organisms are partially permeable membranes.

Active transport

• Active transport is a process whereby substances move from their region of low concentration to their region of high concentration.
• Energy is needed for this process to occur.