Diffusion & Osmosis

• Selectively permeable membranes allow some but not all substances to pass through.
• Water, oxygen, and carbon dioxide can pass through semi-permeable membranes.
• Proteins, sugars, and salts do not pass through semi-permeable membranes freely.
• Diffusion is when molecules move from an area of high concentration to an area of low concentration. e.g smell of perfume
• Diffusion is a passive process and does not require energy.
• Osmosis is the movement of water from a region of high water concentration to an area of low water concentration through a semi-permeable membrane.
• Osmosis is used in food preservation e.g salting meat
• Amoeba prevent from bursting and dying when living in freshwater by using their contractile vacuole. The vacuole expels water out of the amoeba, this is known as osmoregulation.

  
• Cell walls are fully permeable to water, gases and solutes.
• The cell wall regulates turgor pressure in plant cells to prevent bursting.
• Plasmolysis is the process of losing turgor pressure.