Diffusion and Osmosis

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  • B4
    • Diffusion
      • The net movement of particles in a gas or a liquid from and area of high to low concentration resulting in a random movement of  the particles
        • This explains how water, oxygen, and carbon dioxide can enter and leave cells through the cell membrane
      • Leaves are adapted to increase the rate of diffusion of CO2 and O2 by having:
        • Large surface area
        • spaced out special openings called the stomata
        • Gaps between the spongy mesophyll cells
      • Diffusion is not a fixed quantity. It can be increased by...
        • A shorter distance for the molecules to travel
        • A steeper concentration gradient
          • Greater Concentration Gradient = greater difference in concentration between 2 areas
        • A greater surface area for the molecules to diffuse from or into
    • Osmosis
      • A type of diffusion
      • Depends on the presence of a partially permeable membrane
        • That allows the passage of water molecules, but not large molecules such as glucose
      • Osmosis is the movement of water across a partially permeable membrane from an area of high water concentration (dilute solution) to an area of low water concentration (concentrated solution)
      • Osmosis is the consequence of the random moving water molecules, which is not restricted by a partially permeable membrane
      • The net movement of water molecules will be from one were there is very many to one where there are very few


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