Cell membrane and


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Cell membrane and

  1. 1. By: Olivia Leonard, Rebecca Dunlop, Hannah Weagle, and Molly Markos
  2. 3. Cell Membrane Structure <ul><li>Two lipid layers arranged “tail to tail” </li></ul><ul><li>Proteins are free to move and are constantly changing pattern </li></ul><ul><li>Phospholipids </li></ul><ul><li>Tail of the lipid is hydrophobic </li></ul><ul><li>Lipid head is hydrophilic </li></ul>
  3. 4. Cell Membrane Function <ul><li>Defines the limits of the cell </li></ul><ul><li>Proteins scattered in the lipid bilayer are responsible for most of the specialized functions of the membrane </li></ul><ul><li>Proteins protruding from the cell exterior are receptors for hormones </li></ul><ul><li>Other types of protein have the ability to transport molecules inside or outside the cell </li></ul>
  4. 6. Diffusion <ul><li>Unassisted diffusion of solutes through the plasma membrane </li></ul><ul><li>Solutes transported this way are either lipid soluble or are able to pass through the membrane pores </li></ul><ul><li>-example: Chloride Ions </li></ul>
  5. 7. Facilitated Diffusion <ul><li>Provides passage for certain substances that are lipid-insoluble and too large to pass through the membrane pores </li></ul><ul><li>Substances move down their own concentration gradient where the protein membrane channel is used </li></ul><ul><li>Also known as a transport vesicle </li></ul>
  6. 8. Facilitated Diffusion Continued… <ul><li>Some of the proteins in the plasma membrane form channels and act as carriers to move glucose and other solutes passively across the membrane into the cell </li></ul><ul><li>By substances passing in and out of the cell, it saves the cell energy </li></ul><ul><li>Glucose and Oxygen continually moves through the cells, and Carbon Dioxide continually moves out of the cells into the blood </li></ul>
  7. 9. Osmosis <ul><li>The diffusion of water though a selectively permeable membrane such as the plasma membrane </li></ul><ul><li>Since the water is highly polar, it’s repelled by the lipid core of the plasma membrane </li></ul><ul><li>Passes easily though special pores called aquaprins (water pores) created by proteins in the membrane </li></ul><ul><li>Osmosis into and out of the cells is occurring all the time as water moves down its concentration gradient </li></ul>
  8. 10. Osmosis
  9. 12. Example: Sodium Potassium Pump <ul><li>Simultaneously carries Sodium ions (Na+) out and Potassium ions (K+) into the cell and is necessary for normal transmission of impulses by never cells. </li></ul>
  10. 13. Endocytosis (into the cell) <ul><li>Includes those ATP requiring processes that take up, or engulf, extracellular substances by enclosing them in a small membranous vesicle. </li></ul>
  11. 14. Endocytosis Continued… <ul><li>Vesicle or sac forms, it detaches from the plasma membrane and moves into the cytoplasm where it fuses with the lysosome and its contents are digested </li></ul><ul><li>-Pinocytosis: (cell drinking) the cell “gulps” deoplets or extracellular fluid </li></ul><ul><li>-Phagocytosis: (cell eating) </li></ul>
  12. 15. Exocytosis (out of the cell) <ul><li>Moves substances out of the cell </li></ul><ul><li>Cells actively secrete hormones, mucus, and other cell products or ejects certain cellular wastes </li></ul><ul><li>Product to be released is first “packaged” into a small membranous sac (vesicle) </li></ul><ul><li>Vesicle migrates to the plasma membrane </li></ul><ul><li>Fuses, then ruptures spilling sac contents our of the cell </li></ul>