Biology-Diffusion and Osmosis

• Diffusion

  The movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient.
• Hypotonic

  • Low concentration of water in cell
  • High concentration of water in solution surrounding cell
  • Water moves into cell where there is a lower concentration of water along a concentration gradient and across a semi-permeable membrane
  • Cell swells
• Isotonic

  • Same concentration of water inside and outside of the cell
  • No concentration gradient
  • No movement of water
• Hypertonic

  • More water inside the cell that outside the cell
  • Water moves from an area of high concentration in the cell to an area of low concentration outside of the cell down a concentration gradient and across a semi-permeable membrane.
  • Cell shrivels
• Osmosis


  The movement of water from an area of high concentration to an area of low concentration along a concentration gradient and across a semi-permeable membrane.
• Adaptations of the lungs for gas exchange by diffusion

  • Alveoli in the lungs have a cell wall once cell thick- short diffusion
  • Many alveoli in the lungs therefore increasing surface area- more diffusion takes place
  • Breathing moves new air into lungs- maintaining concentration gradient
  • Dense capillary network surrounds alveoli in the lungs- maintains concentration gradient
• Potato RQP- Independent Variable

  Concentration of the sugar solution
• Potato RQP- Dependent Variable

  Mass of potato cylinder
• Potato RPQ-Control Variables

  • Volume of solution
  • Temperature
  • Time
  • Type of sugar
• Active Transport

  The movement of molecules from an area of low concentration to high concentration against a concentration gradient and across a cell membrane. This requires energy from respiration and a protein in the cell membrane

  -Cells that perform active transport require more mitochondria

  e.g. Mineral Ions