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Cell Membranes

Cell Membranes. The cell membrane’s purpose is to control what goes in and what goes out of a cell The cell membrane also provides protection and support. The Lipid Bilayer. The cell membrane is made up primarily of two sheets of lipids called the lipid bilayer

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Cell Membranes

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  1. Cell Membranes

  2. The cell membrane’s purpose is to control what goes in and what goes out of a cell • The cell membrane also provides protection and support

  3. The Lipid Bilayer • The cell membrane is made up primarily of two sheets of lipids called the lipid bilayer • In addition to lipids, some carbohydrates and proteins are embedded in the bilayer. Because of these embedded molecules we refer to the lipid bilayer as a fluid mosaic.

  4. Concentration • How does a cell membrane control what enters and exits a cell? • The concentration of the liquids on either side of the membrane is the key.

  5. Concentration is the measure of the amount of “stuff” (solutes) in any given amount of a solvent. • Concentration = mass of solute / volume of solvent. • 8 grams of an salt in 2 liter of water gives us a concentration of 4 g/L.

  6. Which of these is more concentrated for sugar? • 2 gallon of iced tea with one spoonful of sugar • 3 gallons of iced tea with two spoonfuls of sugar

  7. Which of these is more concentrated for sugar? • 3 gallons of iced tea with two spoonfuls of sugar

  8. Diffusion • http://www.uh.edu/phar2362/animations/simple_diffusion.html

  9. Diffusion • Diffusion is the random spreading out of molecules • In diffusion molecules move from areas of high to areas of low concentration

  10. The cell membrane is only permeable to some substances. It is selectively permeable. • Diffusion can only occur across a cell membrane if that membrane is permeable to the solute in question.

  11. Osmosis • Cell membranes usually permeable to water, so a special kind of diffusion called osmosis can occur. • Osmosis is diffusion of water. • Osmosis moves water from high concentration of water to low concentrations of water.

  12. Concentration of Water • If a water solution is highly concentrated for a solute, it has a low concentration of water.

  13. Which of these is more concentrated for iced tea? • 2 gallon of iced tea with one spoonful of sugar • 3 gallons of iced tea with two spoonfuls of sugar

  14. Which of these is more concentrated for iced tea? • 2 gallon of iced tea with one spoonful of sugar

  15. Where will salt move?

  16. Where will water move?

  17. Transport • When substances move across a cell membrane we call it transport • There are 2 types of transport • Passive • Active

  18. Passive Transport • No energy • Moves from high to low concentration

  19. Facilitated Diffusion • Special protein channels allow substances to pass through a membrane • High to low concentration

  20. Active Transport • Uses energy • Requires transport protein • Low concentrationto high concentration

  21. Tonicity Hypotonic Solution – concentration is lower

  22. Tonicity Isotonic Solution – concentration is equal

  23. Tonicity Hypertonic Solution – concentration is higher

  24. Why can’t we drink sea water? • Salt water is hypertonicto our cells

  25. Water intoxication • Drinking extremely large amounts of water in a short time period can lead to death • Our cells are hypotonic to pure water

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