Passive Transport


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  • What is meant by the word transport? Moving substances across the cell membrane
  • What is the cell membrane made of? Lipids make it polar--> oxygen and co2 can readily pass through Small molecules can pass through protein pores
  • Spray aerosol into the corner of the classroom Kinetic energy --> Particles are constantly moving and bumping into each other Start a mosh pit in the corner of the classroom In the absence of outside influence diffusion will continue until equilibrium is reached
  • Molecules may be too large or not soluble in lipids --> glucose
  • Hypotonic solutions are good Cells adapt by pumping water or solutes out of the cytosol (contractile vacuoles or solute pumps) Plants love hypotonic environments --> turgor pressure Hypertonic solutions are bad…emkay Results in the loss of water --> plasmolysis Some cells cannot adjust to changes in environment (rbc’s) --> cytolysis or “cell bursting “ may result
  • Macromolecules, nutrients, large quantities of small molecules
  • The vesicles then fuse with other membrane bound organelles within the cell
  • Phagocytosis can be used to ingest bacteria or viruses that invade the body! Pic --> white blood cell ingestng bacteria
  • Passive Transport

    1. 1. Cellular Transport ‘ 07 Biology
    2. 2. 2 Types: <ul><li>Passive </li></ul><ul><li>No energy! </li></ul><ul><li>Active </li></ul><ul><li>Energy! </li></ul>
    3. 3. Passive Transport <ul><li>Substances are allowed to cross the cell membrane without any input of energy </li></ul><ul><li>Remember: The cell membrane is “selectively permeable” </li></ul>
    4. 4. Types of Passive Transport <ul><li>Diffusion </li></ul><ul><li>Facilitated Diffusion </li></ul><ul><li>Osmosis </li></ul>
    5. 5. Diffusion <ul><li>Movement of molecules from areas of high concentration to low </li></ul><ul><li>How does it work? </li></ul><ul><li>“ Kinetic energy” (energy in motion) </li></ul><ul><li>Concentration gradient- caused by a difference in concentration </li></ul><ul><li>Diffusion results in equilibrium (all molecules occupy the same amount of space) </li></ul>
    6. 6. Facilitated Diffusion <ul><li>Some molecules are helped across the cell membrane by carrier proteins </li></ul><ul><li>No energy is required in this process </li></ul>
    7. 7. Osmosis <ul><li>The diffusion of water across the cell membrane </li></ul><ul><li>The direction of osmosis depends on the concentration of solutes inside and outside the cell </li></ul>
    8. 8. Osmosis (continued) <ul><li>Hypotonic- concentration of solutes outside the cell is lower than the concentration inside </li></ul><ul><li>Hypertonic- concentration outside is higher than inside </li></ul><ul><li>Isotonic- concentrations inside and out are equal </li></ul>
    9. 9. Direction of Osmosis
    10. 10. Active Transport <ul><li>Sometimes cells must move molecules against the concentration gradient </li></ul><ul><li>This process requires energy (ATP) and special protein “pumps” </li></ul>
    11. 11. Sodium-Potassium Pump <ul><li>Special proteins within the membrane that transport Na+ and K- ions </li></ul><ul><li>Some cells must have a higher concentration of Na+ ions outside of the cell and a higher concentration of K- ions inside the cell </li></ul><ul><li>2 Potassiums are brought in for every 3 Sodiums removed </li></ul>
    12. 12. Sodium-Potassium Pump
    13. 13. Movement In Vesicles <ul><li>Some molecules are too big to be transported across the cell membrane by passive and active transport </li></ul><ul><li>Endocytosis- “cell eating” </li></ul><ul><li>Exocytosis- “cell pooping” </li></ul>
    14. 14. Endocytosis <ul><li>Process by which cells ingest macromolecules, fluids, large particles and even other cells </li></ul><ul><li>These molecules are enclose in a bubble of membrane ( vesicle ) that pinches away from the cell membrane </li></ul>
    15. 15. Endocytosis (continued) <ul><li>Pinocytosis- ingestion of small particles and fluid </li></ul><ul><li>Phagocytosis- ingestion of large molecules or other cells </li></ul>
    16. 16. Exocytosis <ul><li>Process by which waste and large particles are released from the cell </li></ul><ul><li>A vesicle will fuse with the membrane, releasing its contents into the extra cellular environment </li></ul>
    17. 17. Endocytosis/Exocytosis