Cellular Transport

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Cell Transport and The Plasma Membrane

  1. 1. Cellular Transport Notes
  2. 2. About Cell Membranes 1.All cells have a cell membrane 2.Functions: a.Controls what enters and exits the cell to maintain an internal balance called homeostasis b.Provides protection and support for the cell TEM picture of a real cell membrane.
  3. 3. 3.Structure of cell membrane Phospholipid Bilayer -2 layers of phospholipids a.Phosphate head is polar (water loving) b.Fatty acid tails non-polar (water fearing) c.Proteins embedded in membrane About Cell Membranes (continued) Phospholipid Lipid Bilayer
  4. 4. Proteins Membrane move Polar heads love water & dissolve. Non-polar tails hide from water. Carbohydrate cell markers Fluid Mosaic Model of the cell membrane
  5. 5. • 4. Cell membranes have pores (holes) in it a.Selectively permeable: Allows some molecules in and keeps other molecules out b.The structure helps it be selective! About Cell Membranes (continued) Pores
  6. 6. Outside of cell Inside of cell (cytoplasm) Lipid Bilayer Proteins Transport Protein Phospholipids Carbohydrate chains Structure of the Cell Membrane Go to Section: Animations of membrane structure
  7. 7. Types of Cellular Transport • Passive Transport cell doesn’t use energy 1. Diffusion 2. Facilitated Diffusion 3. Osmosis • Active Transport cell does use energy 1. Protein Pumps 2. Endocytosis 3. Exocytosis high low This is gonna be hard work!! high low Weeee!! ! •Animations of Active Transport & Passive Transport
  8. 8. Passive Transport • cell uses no energy • molecules move randomly • Molecules spread out from an area of high concentration to an area of low concentration. • (HighLow) • Three types:
  9. 9. Passive Transport: 1. Diffusion 1. Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) • Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm Simple Diffusion A
  10. 10. 2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane a.Transport Proteins are specific – they “select” only certain molecules to cross the membrane b.Transports larger or charged molecules Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer) Passive Transport: 2. Facilitated Diffusion Carrier Protein A B
  11. 11. • 3.Osmosis: diffusion of water through a selectively permeable membrane • Water moves from high to low concentrations •Water moves freely through pores. •Solute (green) to large to move across. Osmosis animation Passive Transport: 3. Osmosis
  12. 12. Active Transport •cell uses energy (in the form of ATP) •actively moves molecules to where they are needed •Movement from an area of low concentration to an area of high concentration •(Low  High) •Three Types:
  13. 13. 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!
  14. 14. Types of Active Transport • 2. Endocytosis: taking bulky material into a cell • Uses energy • Cell membrane in-folds around food particle • “cell eating” • forms food vacuole & digests food • This is how white blood cells eat bacteria!
  15. 15. 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
  16. 16. Dynamic Equilibrium • In some cases particles or water are constantly moving with no change and maintaining an equilibrium
  17. 17. Example Test Question 1. Which of the following pieces of evidence would suggest that a substance entered a cell via active transport as opposed to passive transport? (SC.912.L.14.2) a.The substance moved from a high concentration to a low concentration b.The substance moved across the membrane without the use of energy c.ATP was required for transport d.None of the above
  18. 18. 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 (cytolysis)! • Great Video on Hypo, Hyper, and Iso-tonic Solutions
  19. 19. 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 from inside the cell into the solution: Cell shrinks (Plasmolysis)! • Osmosis Animations for isotonic, hypertonic, and hypotonic solutions shrinks
  20. 20. 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
  21. 21. What type of solution are these cells in? A CB Hypertonic Isotonic Hypotonic
  22. 22. How Organisms Deal with Osmotic Pressure • Paramecium (protist) removing excess water video •Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. •A protist like 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.
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