1. Cell Membranes & Movement Across ThemRegents Biology2006-2007

2. Cell (plasma) membrane Cells need an inside & an outside separate cell from its environmentcell membrane is the boundaryIN food - sugars - proteins - fats salts O2 H2O Regents BiologyOUT waste - ammonia - salts - CO2 - H2O products - proteinscell needs materials in & products or waste out 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 dont mix!! What substance do you know that doesnt mix with water? Regents Biology 4. Lipids of cell membrane Membrane is made of special kind of lipid phospholipids split personalityattracted to water Membrane is a double layer phospholipid bilayerphosphateinside cell lipidoutside cellRegents Biologyrepelled by water 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 outSo what needs to get across the membrane? sugar lipidsRegents BiologyaaO2H2Osaltwaste 6. Crossing the cell membrane What molecules can get through the cell membrane directly? fats and oils can pass directly throughinside cell wasteoutside cell Regents Biologylipid saltsugar aaH2Obut what about other stuff? 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 cellwaste salt Regents BiologyH2Oaasugaroutside cell 8. How do you build a semi-permeable cell membrane? Channels are made of proteins proteins both like water & like lipidsbi-lipid membraneRegents Biologyprotein channels in bi-lipid membrane 9. Protein channels Proteins act as doors in the membrane channels to move specific molecules through cell membrane HIGHLOW Regents Biology 10. Movement through the channel Why do molecules move through membrane if you give them a channel? HIGH ?LOW ? Regents Biology 11. Molecules move from high to low Diffusion move from HIGH to LOW concentrationRegents Biology 12. Diffusion Move from HIGH to LOW concentration passive transport no energy needed Regents Biologydiffusiondiffusion of waterosmosis 13. Simple Diffusion Move from HIGH to LOW fat inside cellLOWfat fatfat fatfatWhich way will fat move?HIGH outside cell fat Regents Biologyfat fatfatfat fatfat fat 14. Facilitated Diffusion Move from HIGH to LOW through a channel sugar sugar sugar sugar inside cell sugar sugarLOWWhich way will sugar move?HIGH outside cell sugar Regents Biologysugarsugarsugarsugar sugar sugar 15. Diffusion Move from HIGH to LOW concentration directly through membrane simple diffusion no energy neededhelp through a protein channel facilitated diffusion (with help) no energy needed HIGHRegents BiologyLOW 16. Simple vs. facilitated diffusion simple diffusion inside celllipidfacilitated diffusion inside cellH2Oprotein channeloutside cell Regents Biologyoutside cellH2O 17. Active transport Cells may need molecules to move against concentration hill need to pump uphill from LOW to HIGH using energyprotein pump requires energy ATP ATPRegents Biology 18. Transport summary simple diffusion facilitated diffusionactive transport Regents BiologyATP 19. Osmosis Movement of Water Across Cell MembraneRegents Biology2006-2007 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 membraneRegents Biology 21. Keeping water balance Cell survival depends on balancing water uptake & water loss freshwaterRegents Biologybalancedsaltwater 22. 1Keeping right amount of water in cell FreshwaterKABOOM!freshwatera cell in fresh water high concentration of water around cell cell gains water example: Paramecium problem: cells gain water,swell & can burst water continually entersNo problem, hereParamecium cell solution: contractile vacuole pumps water out of cell Regents Biology 23. Controlling water Contractile vacuole in ParameciumRegents Biology 24. 2Keeping right amount of water in cell SaltwaterIm shrinking, Im shrinking!a cell in salt water low concentration of water around cell cell loses waterexample: shellfish problem: cell loses water in plants: plasmolysis in animals: shrinking cell solution: take up waterRegents BiologyI will survive!saltwater 25. 3Keeping right amount of water in cell Balanced conditions Thats better!no difference in concentration of water between cell & environment cell in equilibrium example: blood problem: none water flows acrossmembrane equally, in both directions volume of cell doesnt change Regents BiologyI could be betterbalanced 26. Ice Fishing in BarrowQuickTime and a YUV420 codec decompressor are needed to see this picture.Regents Biology