Explanation of Diffusion

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  • Explanation of Osmosis
    • OSMOSIS
      • CELLS AND MOVEMENT IN AND OUT OF THEM
        • DIFFUSION
          • Explanation of Diffusion
            • all particles are constanlty in motion due to the kinetic energy that they possess
          • Definition: THE NET MOVEMENT OF MOLECULES OR IONS FROM A REGION WHERE THEY ARE MORE HIGHLY CONCENTRATED TO ONE WHERE THE CONCENTRATION IS LOWER.
        • FACILITATED DIFFUSION
          • It relies on the inbuilt motion (kinetic energy) of diffusing molecules.
          • It occurs down a concentration gradient, it occurs on specific points on the plasma membrane where there are special protein molecules, the protains form water channels across the membrane
          • these allow water soluble ions and molecules such as glucos, to pass through
        • ACTIVE TRANSPORT
          • THE MOVEMENT OF MOLECULES OR IONS INTO OR OUT OF A CELL FROM A REGION OF LOWER CONCENTRATION TO A REGION OF HIGHER CONECNTRATION USING ENERGY AND CARRIER MOLECULES
          • Active Transport uses ATP in two ways:
            • by using ATP to directly move molecules
            • by using a concentratioh gradient that has already been set up by direct active transport. This is Co- Transport
      • THE PASSAGE OF WATER FROM A REGION WHERE IT HAS HIGH WATER POTENTIAL TO A REGION WHERE IT HAS A LOWER WATER POTENTIAL THROUGH A PARTIALLY PERMEABLE MEMBRANE.
    • the solution on the left has a low concentration of solute molecules while the solution on the right has a high concentration of solute molecules
      • Both the solute and water molecules are in random motion doe to their kinetic energy
        • The partcially permeable plasma membrane, howeever only allows water molecules across it and not solute molecules
          • the water molecules diffuse from the left hand side which has the higher water potential to the right hand side, which has lower water potential.
            • at the point where water potentials on either side of the plasma membrane are equal, a dynamic equilibrium is established and there is no net movement of water

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