Diffusion osmosis active transport 🧬

• Osmosis


  The event of water molecules across a partially permeable membrane from a region of high water concentration to a region of lower water concentration
• A partially permeable membrane is one with very small holes in it, so small that only water molecules can pass through
• Osmosis


  1. Water molecules actually pass both ways through the membrane during osmosis

  2. There are more water molecules on one side than the other

  3. This leads to a net flow of water into the region with fewer water molecules

  4. The solution on that side gets more dilute
• Cell fluid


  The fluid that surrounds the cells in the body, basically just water with some dissolved stuff
• If a cell is short of water

  Osmosis will help the cell gain water
• You can investigate diffusion in a non-living system
• You can investigate osmosis in both living and non-living systems
• Investigating osmosis in a living system (potato cylinders)

  1. Set up an experiment with potato cylinders, some in concentrated solution and some in dilute

  2. Measure the change in mass of the cylinders over time

  3. The cylinders in concentrated solution will lose water by osmosis, the ones in dilute solution will gain water
• Investigating osmosis in a non-living system (Visking tubing)

  1. Put some Visking tubing over the end of a glass tube

  2. Add a sugar solution down the tube into the Visking tubing

  3. Put the tubing in a beaker of water

  4. Observe the change in volume of the solution in the tube over time
• Four factors affecting movement of substances

  • Concentration gradient
  • Temperature
  • Surface area to volume ratio
  • Active transport
• Active transport works against a concentration gradient
• Diffusion is the movement of particles from an area of high concentration to low concentration until equilibrium is reached.
• Osmosis is the diffusion of water across a partially permeable membrane, driven by a concentration gradient.
• Rate of diffusion also depends on temperature - higher temperatures mean faster diffusion because particles move around more quickly.