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Cell Membrane And Cell Transport Notes New

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  • 1. Cellular Transport Notes
  • 2. About Cell Membranes
    • All cells have a cell membrane
    • Functions :
      • Controls what enters and exits the cell to maintain an internal balance called homeostasis
      • Provides protection and support for the cell
    TEM picture of a real cell membrane.
  • 3. What is the purpose of cellular transport?
    • Homeostasis depends upon appropriate movement of materials across the cell membrane.
      • Required materials must pass into the cells so they can be utilized.
        • Ex. Oxygen and glucose for cellular respiration
      • Waste materials must pass out of the cells as they are produced
        • Ex. The CO 2 produced as a waste product of cellular respiration
    • The cell membrane regulates the passage of materials into and out of the cell.
      • Needed materials move in
      • Excess materials move out
  • 4. How?
    • Each individual cell exists in a fluid environment, and the cytoplasm within the cell also has a fluid environment. The presence of a liquid makes it possible for substances (such as nutrients, oxygen, and waste products) to move into and out of the cell.
    • A cell membrane is semipermeable (selectively permeable), meaning that some substances can pass directly through the cell membrane while other substances can not .
    • Materials can enter or exit through the cell membrane by passive transport or active transport.
    Membrane movement animation
  • 5. Types of Cellular Transport
    • Passive Transport
    • cell doesn’t use energy
      • Diffusion
      • Facilitated Diffusion
      • Osmosis
    • Active Transport
    • cell does use energy
      • Protein Pumps
      • Endocytosis
      • Exocytosis
    • Animations of Active Transport & Passive Transport
    high low This is gonna be hard work!! high low Weeee!!!
  • 6. Passive Transport
    • cell uses no energy
    • molecules move randomly
    • The random motion of molecules occurs along the concentration gradient meaning molecules spread out from an area of high concentration to an area of l ow concentration .
    • (High  Low)
    • Three types:
  • 7. 3 Types of Passive Transport
    • 1. Diffusion – is the spreading out of molecules across a cell membrane until they are equally concentrated.
    • 2. Facilitative Diffusion – diffusion with the help of transport proteins
    • 3. Osmosis – diffusion of water
  • 8. Passive Transport: 1. Diffusion
    • Diffusion : random movement of particles from an area of high concentration to an area of low concentration .
    • Diffusion continues until all molecules are evenly spaced ( equilibrium is reached)- Note: molecules will still move around but stay spread out.
    Simple Diffusion Animation
  • 9.
    • Facilitated diffusion : diffusion of specific particles along the concentration gradient (High  Low) with the help of transport proteins found in the membrane
      • Transport Proteins are specific – they “ select ” only certain molecules to cross the membrane
      • Transports larger or charged molecules that cannot pass through the membrane on their own
      • Glucose is an example of a molecule that passes into the cell through facilitated diffusion
    Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Passive Transport : 2. Facilitated Diffusion Carrier Protein A B
    • http://bio.winona.edu/berg/Free.htm
  • 10. High Concentration Low Concentration Cell Membrane Glucose molecules Protein channel Passive Transport: 2. Facilitated Diffusion Go to Section: Transport Protein Through a  Cellular Transport From a- High Low
    • Channel Proteins animations
  • 11.
    • Osmosis : diffusion of water through a selectively permeable membrane
    • Water moves from a high concentration of water to a low concentration of water
    • Because water is so small and in such abundance , the cell cannot control its movement through the cell membrane.
    Osmosis animation Passive Transport: 3. Osmosis
  • 12. Effects of Osmosis on Life
    • Water moves freely through pores.
    • Solute (green) too large to move across.
    • Reminder:
      • Solute : what is being dissolved
      • Solvent : what dissolves the solute
        • In salt water, the solute is the salt and the solvent is the water
  • 13. Hypotonic Solution Hypotonic : The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result : Water moves from the solution to inside the cell): Cell Swells and bursts open ( lyse )!
    • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
  • 14. Hypertonic Solution Hypertonic : The solution has a higher concentration of solutes and a lower concentration of water than inside the cell . (High solute; Low water) Result : Water moves out of the cell into the solution: Cell shrivels !
    • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
    shrinks
  • 15. Isotonic Solution Isotonic : The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result : Water moves equally in both directions and the cell remains same size! ( Dynamic Equilibrium )
    • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions
  • 16. In what type of solution are these cells? A C B Hypertonic Isotonic Hypotonic
  • 17. How Organisms Deal with Osmotic Pressure
    • Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure .
    • A protist like the paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.
    • Salt water fish pump salt out of their specialized gills so they do not dehydrate.
    • Animal cells are bathed in blood . Kidneys keep the blood isotonic by remove excess salt and water.
    • Paramecium (protist) removing excess water video
  • 18. Active Transport
    • Requires the cell to use energy
    • Actively moves molecules to where they are needed
    • Molecules move against the concentration gradient - from an area of low concentration to an area of high concentration
    • (Low  High)
    • Three Types :
  • 19. Types of Active Transport
    • 1. Protein Pumps -transport proteins that require energy to do work
      • Example: Sodium / Potassium Pumps are important in nerve responses.
    Sodium Potassium Pumps (Active Transport using proteins) Protein changes shape to move molecules: this requires energy !
  • 20. Types of Active Transport
    • 2. Endocytosis : taking bulky material into a cell by forming a vesicle
      • Uses energy
      • Cell membrane in-folds around food particle
      • “ cell eating ”
      • forms food vacuole & digests food
      • This is how white blood cells eat bacteria !
  • 21. Types of Active Transport
    • 3. Exocytosis : Forces material out of cell in bulk
      • Membrane surrounding the material fuses with cell membrane
      • Cell changes shape – requires energy
      • Ex: Hormones or wastes released from cell
    Endocytosis & Exocytosis animations