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  • 1. Chapter 4 Notes Cells and Their Environment
  • 2. Molecules need to move across membranes in cells… Image modiified from: IN food carbohydrates sugars, proteins amino acids lipids salts, O 2 , H 2 O OUT waste ammonia salts CO 2 H 2 O products How does that happen?
  • 3. I. Passive Transport
    • Passive Transport -the movement of substances across the cell membrane without the use of energy by the cell.
    • There are many types of passive transport:
  • 4. A. Diffusion
    • Diffusion - is the movement of a substance from an area of high concentration to an area of low concentration.
    • Diffusion will eventually cause substances to be balanced (equilibrium) on both sides of the cell membrane .
      • Ex: ink or food coloring moving through water.
  • 5. Diffusion-high to low concentration. Animatioin from:
  • 6. B. Osmosis
    • Osmosis - is the diffusion of water molecules across a selectively permeable membrane. ( Egg Experiment )
  • 7.  
  • 8.
    • 1. Hypotonic -solute outside cell less than inside; water moves into cell; cell swells
    • 2. Hypertonic- solute outside cell greater than inside; water moves out of cell; cell shrinks
    • 3. Isotonic -solute outside cell equals inside; no net movement of water.
  • 9. HYPOTONIC ISOTONIC HYPERTONIC solute outside ‹ inside Net movement of water into cell Animal cells: swell & burst = CYTOLYSIS Plant cells increase TURGOR PRESSURE solute outside = inside Net movement of water in and out of cell is equal No change in size solute outside > inside Net movement of water out of cell Animal cells: shrink = CRENATION Plant cells: can’t shrink due to cell wall Cell membrane pulls away from cell wall= PLASMOLYSIS
  • 10. C.Facilitated Diffusion
    • Facilitated Diffusion -when a membrane protein helps to transport a substance across a cell membrane.
  • 11. Types of Facilitated Diffusion
      • 1. Ion Channels -proteins that have a pore through which ions such as sodium, calcium, potassium can cross the cell membrane.
    Animation from:
  • 12. Types of FacilitatedDiffusion 2. Carrier protein -proteins that bind to specific substances, carry it across the cell membrane , and release it. Animation from:
  • 13. II. Active Transport
    • Active Transport-the movement of a substance into an area of higher concentration by using energ y from the cell in the form of ATP .
    • There are many types of active transport:
  • 14.
      • 1. Sodium-Potassium pump
        • sodium ions are pumped out of the cell.
        • Potassium ions are pumped into the cell.
  • 15.
    • 2. Endocytosis -substances that are too large to move into the cell membrane are moved by a vesicle that forms around it. / Animation from:
  • 16.
    • 3. Exocytosis -substances that are too large to move out of the cell membrane are released by a vesicle that forms around it.
  • 17.
    • 4. Membrane Receptor Proteins-proteins that help cell communicate with each other.