diffusion + osmosis

• Diffusion


  The net movement of particles from an area of higher concentration to an area of lower concentration
• Diffusion


  1. Molecules move about randomly

  2. Molecules spread out over time

  3. Molecules become evenly distributed
• Diffusion can happen in both gases and liquids
• Partially permeable membrane


  Only some molecules can diffuse through, like water, glucose, and amino acids. Larger molecules like proteins and starch cannot fit through.
• Diffusion is a passive process that does not require energy from the cell
• Factors affecting rate of diffusion

  • Concentration gradient
  • Temperature
  • Surface area
• Concentration gradient


  The difference in concentration between two places
• Larger concentration gradient


  Higher rate of diffusion
• Temperature


  Higher temperatures give particles more energy, resulting in faster movement and higher rate of diffusion
• Surface area


  Larger surface area allows more particles to diffuse in and out at once, resulting in higher rate of diffusion
• Osmosis


  The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
• Water concentration


  The amount of water as compared to the other molecules like sugars or salts that are dissolved in that water
• Solutes are the dissolving molecules in water
• Higher solute concentration


  Lower water concentration
• Lower solute concentration


  Higher water concentration
• Osmosis in cells


  Water particles diffuse from outside the cell (higher water concentration) into the cell (lower water concentration) across the partially permeable cell membrane
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