Cell Membrane And Cell Transport Notes New


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Cell Membrane And Cell Transport Notes New

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