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Cell Membranes          &Movement Across Them                       2006-
Cell (plasma) membrane  Cells need an inside & an outside…         separate cell from its environment         cell memb...
Building a membrane    How do you build a barrier that keeps       the watery contents of the cell separate       from th...
Lipids of cell membrane  Membrane is made of special kind of lipid      phospholipids      “split personality”         ...
Semi-permeable membrane Cell membrane controls what gets in or out Need to allow some materials — but not all  — to pass...
Crossing the cell membrane What molecules can get through the cell  membrane directly?     fats and oils can pass direct...
Cell membrane channels  Need to make “doors” through membrane       protein channels allow substances in & out         ...
How do you build a semi-permeablecell membrane?  Channels are made of proteins     proteins both “like” water & “like” l...
Protein channels  Proteins act as doors in the membrane      channels to move specific molecules       through cell memb...
Movement through the channel  Why do molecules move through  membrane if you give them a channel?       ?      HIGH      ...
Molecules move from high to low  Diffusion     move from HIGH to LOW concentration
Diffusion  Move from HIGH to LOW concentration    passive transport    no energy needed                         diffusi...
Simple Diffusion  Move from HIGH to LOW                 fat                               fat                fat         ...
Facilitated Diffusion Move from HIGH to LOW through a channel                            sugar sugar                     ...
Diffusion Move from HIGH to LOW concentration     directly through membrane       simple diffusion       no energy nee...
Simple vs. facilitated diffusion   simple diffusion      facilitated diffusion               lipidinside cell            i...
Active transport  Cells may need molecules to move  against concentration “hill”      need to pump “uphill”        from...
Transport summary              simple              diffusion              facilitated              diffusion              ...
OsmosisMovement of Water AcrossCell Membrane                           2006-
Osmosis Water is very important, so we talk about  water separately Osmosis     diffusion of water from HIGH concentrat...
Keeping water balance  Cell survival depends on balancing   water uptake & water loss     freshwater   balanced   saltwater
1    Keeping right amount of water in cell     Freshwater                                    freshwater                  ...
Controlling water  Contractile vacuole in Paramecium
2    Keeping right amount of water in cell      Saltwater                       I’m shrinking,    saltwater              ...
3    Keeping right amount of water in cell      Balanced conditions                That’s       balanced                 ...
Ice Fishing in Barrow
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Cell Membranes and Transport - Biology

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Transcript of "Cell Membranes and Transport - Biology"

  1. 1. Cell Membranes &Movement Across Them 2006-
  2. 2. Cell (plasma) membrane  Cells need an inside & an outside…  separate cell from its environment  cell membrane is the boundary IN OUT food waste - sugars - ammonia - proteins - salts - fats - CO2 salts - H2O O2 products H2 O - proteins cell needs materials in & products or waste out
  3. 3. Building a membrane  How do you build a barrier that keeps the watery contents of the cell separate from the watery environment?  FATS   LIPIDS  Remember: oil & water don’t mix!!What substancedo you knowthat doesn’t mixwith water?
  4. 4. Lipids of cell membrane  Membrane is made of special kind of lipid  phospholipids  “split personality” “attracted to water”  Membrane is a double layer  phospholipid bilayer phosphate inside cell lipid “repelled by water” outside cell
  5. 5. Semi-permeable membrane Cell membrane controls what gets in or out Need to allow some materials — but not all — to pass through the membrane  semi-permeable  only some material can get in or out So what needs to get across the membrane?sugar lipids aa O2 H 2O salt waste
  6. 6. Crossing the cell membrane What molecules can get through the cell membrane directly?  fats and oils can pass directly through lipid inside cell waste salt but… sugar aa H 2O what about outside cell other stuff?
  7. 7. Cell membrane channels  Need to make “doors” through membrane  protein channels allow substances in & out  specific channels allow specific material in & out  H2O channel, salt channel, sugar channel, etc.inside cell H 2O aa sugarwaste salt outside cell
  8. 8. How do you build a semi-permeablecell membrane?  Channels are made of proteins  proteins both “like” water & “like” lipids bi-lipid protein channels membrane in bi-lipid membrane
  9. 9. Protein channels  Proteins act as doors in the membrane  channels to move specific molecules through cell membrane HIGH LOW
  10. 10. Movement through the channel  Why do molecules move through membrane if you give them a channel? ? HIGH ? LOW
  11. 11. Molecules move from high to low  Diffusion  move from HIGH to LOW concentration
  12. 12. Diffusion  Move from HIGH to LOW concentration  passive transport  no energy needed diffusion of water diffusion osmosis
  13. 13. Simple Diffusion  Move from HIGH to LOW fat fat fat Which way inside cell will fat move? fat fat fat LOW HIGH fat outside cell fat fat fat fat fat fat fat
  14. 14. Facilitated Diffusion Move from HIGH to LOW through a channel sugar sugar sugar sugar inside cell sugar sugar LOW Which way will sugar move? HIGH outside cell sugar sugar sugar sugar sugar sugar sugar
  15. 15. Diffusion Move from HIGH to LOW concentration  directly through membrane  simple diffusion  no energy needed  help through a protein channel  facilitated diffusion (with help)  no energy needed HIGH LOW
  16. 16. Simple vs. facilitated diffusion simple diffusion facilitated diffusion lipidinside cell inside cell H 2O protein channel H 2Ooutside cell outside cell
  17. 17. Active transport  Cells may need molecules to move against concentration “hill”  need to pump “uphill”  from LOW to HIGH using energy  protein pump  requires energy  ATP ATP
  18. 18. Transport summary simple diffusion facilitated diffusion active ATP transport
  19. 19. OsmosisMovement of Water AcrossCell Membrane 2006-
  20. 20. Osmosis Water is very important, so we talk about water separately Osmosis  diffusion of water from HIGH concentration of water to LOW concentration of water  across a semi-permeable membrane
  21. 21. Keeping water balance  Cell survival depends on balancing water uptake & water loss freshwater balanced saltwater
  22. 22. 1 Keeping right amount of water in cell  Freshwater freshwater KABOOM!  a cell in fresh water  high concentration of water around cell  cell gains water  example: Paramecium  problem: cells gain water, swell & can burst No problem,  water continually enters here Paramecium cell  solution: contractile vacuole  pumps water out of cell
  23. 23. Controlling water  Contractile vacuole in Paramecium
  24. 24. 2 Keeping right amount of water in cell  Saltwater I’m shrinking, saltwater I’m shrinking!  a cell in salt water  low concentration of water around cell  cell loses water  example: shellfish  problem: cell loses water I will  in plants: plasmolysis survive!  in animals: shrinking cell  solution: take up water
  25. 25. 3 Keeping right amount of water in cell  Balanced conditions That’s balanced better!  no difference in concentration of water between cell & environment  cell in equilibrium  example: blood  problem: none  water flows across I could be better… membrane equally, in both directions  volume of cell doesn’t change
  26. 26. Ice Fishing in Barrow
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