Cell membrane powerpoint diffusion and osmosis revised


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Cell membrane powerpoint diffusion and osmosis revised

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  2. 2. Cell Boundaries<br />Chapter 6<br />
  3. 3. What are boundaries?<br />We have borders surrounding countries<br />We have boundaries on a playing field<br />Why are borders important?<br />
  4. 4. What are the borders of a cell?<br />Cell membrane<br />Thin, flexible barrier<br />Cell wall<br />Plant, algae, fungi, prokaryotes<br />Strong supporting layer<br />
  5. 5. Cell Membrane<br />What does it do for cell?<br />Controls what goes in and out <br />Regulates molecules moving from one liquid side of the cell to the other liquid side of the cell<br />Protects<br />Supports<br />
  6. 6. Cell Membrane<br />Lipid bilayer<br />What are lipids?<br />What does bi- mean?<br />What’s a layer?<br />A cell membrane is made of two<br /> layers of lipid molecules<br />
  7. 7. Cell membrane<br />Phospholipids bilayer<br />Made of a negatively charged phosphate “head”<br />PO43-<br />Attracts water because the phosphate is charged (-)<br />Water is a polar , slightly positive ends and slightly negative ends<br />Attached to the phosphate group are 2 fatty acid chains<br />Hydrophobic= don’t like water<br />So the inside of the cell membrane doesn’t let water in but the outside allows cells to be dissolved in aqueous environments<br />
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  9. 9. Other things in the membrane…<br />Proteins embedded in lipid bilayer<br />Carbohydrates attached to proteins<br />So many different molecules in membrane, we call it a “mosaic” of different molecules<br />
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  11. 11. Proteins<br />Proteins help things get across membrane<br />Kinda like a pump<br />
  12. 12. Carbohydrates…<br />Chemical identification cards<br />“ID” card of cell<br />Helps individual cells id each other<br />
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  14. 14. Cell Walls<br />Outside cell membrane (does NOT replace membrane!!!)<br />Plants, algae, fungi, prokaryotes<br />Have pores to allow things in<br />Function: SUPPORT and PROTECT<br />
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  16. 16. Cell walls made of…<br />Protein and carbs<br />Plant cell walls made up of CELLULOSE<br />This is a tough carbohydrate<br />Wood and paper<br />
  17. 17. A biological membrane<br />Cells exist in liquid environments<br />Things need to get in and out of cell<br />Different ways to do this….<br />The Cell Membrane<br />
  18. 18. Concentration (conc.)<br />Solution<br />Mix of 2 or more substances<br />Solutes<br />Substance dissolved in solution<br />Concentration <br />Molarity(M) is # of Moles of a substance per liter of solution<br />6.02 x 1023 “small things” (molecules, atoms, ions, electrons, ions, etc)<br />Moles is a unit for measuring EXTREMELY small things<br />is mass of SOLUTE in a given volume of solution (g/L)<br />What is the concentration of 12 grams of salt dissolved in 3 liters of water?<br />12g/3L= 4g/L<br />
  19. 19. Diffusion<br />Particles constantly move<br />Collide randomly<br />Spread out randomly<br />Diffusion is moving from area of HIGH conc. to area of LOW conc.<br />This is what we call the CONCENTRATION GRADIENT<br />
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  21. 21. Equilibrium<br />When the conc. Of a system is the same throughout <br />(same conc. on both sides)<br />
  22. 22. What’s this have to do with cells?<br />Cell have liquid inside and are found in liquid environment<br />We have substances (solutes) inside and outside cell<br />Unequal concentrations means we get DIFFUSION!!!<br />B/c diffusion depends on random particle movements, substances diffuse across membranes without requiring the cell to use energy<br />
  23. 23. What happens when we reach equilibrium?<br />Particles continue moving across membrane but in both directions!***No more changes in concentration<br />
  24. 24. Problems for diffusion…<br />Things too large<br />Charged molecules<br />Positive/negative<br />Opposites attract but likes do not…<br />These all present serious problems for things getting across membranes…<br />
  25. 25. If things can cross a membrane we call the membrane PERMEABLE<br />If things canNOT cross a membrane we call the membrane IMPERMEABLE<br />
  26. 26. Biological membranes are…<br />SEMI-PERMEABLE<br />Aka…<br />Selectively permeable<br />Cell membranes are picky<br />
  27. 27. Osmosis<br />Water (H2O) can pass easily through most biological membranes<br />Def: <br />Diffusion of Water through a semi-permeable membrane<br />
  28. 28. How Osmosis works…<br />We have water molecules and some other molecules, let’s say sugar<br />If we have more water on one side of the membrane (HIGH conc. of H2O), then the water will diffuse across…<br />Membrane will let water thru but not sugar <br />Water can move back and forth (not sugar)<br />
  29. 29. Water moves from areas of HIGH conc. To areas of LOW conc.<br />Water moves across till equilibrium is reached<br />Isotonic: <br />when conc. Of both solutions is equal<br />Hypertonic: “above strength”<br />When we begin with more sugar in water<br />More concentrated sugar solution on side A<br />Hypotonic: “below strength”<br />When we end with less sugar <br />Dilute sugar solution on side A<br />
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  31. 31. Osmotic Pressure<br />Central vacuole fills with water and exerts and out ward pressure on cell membrane and cell wall<br />Cell wall does NOT allow cell to expand past a certain size<br />
  32. 32. How do big molecules diffuse across a membrane so quickly if the membrane is selectively permeable?<br />
  33. 33. Facilitated Diffusion<br />What does facilitate mean?<br />Proteins are the extra help<br />“escorts” across the membrane<br />We call these protein channels…<br />Allow specific things thru<br />
  34. 34. Facilitated Diffusion (continued)<br />FAST<br />SPECIFIC<br />Still diffusion so we only see it from high concentration to low<br />Does NOT require energy<br />
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  36. 36. What about when we want to go against the concentration?<br />(From low concentration to high?)<br />
  37. 37. What do we need???<br />ENERGY!!!!<br />
  38. 38. ACTIVE transport<br />Process that moves molecules against the concentration gradient<br />Requires ENERGY<br />A protein pumps small molecules and ions across a cell membrane against the conc. Gradient<br />Electrochemical gradient<br />membrane potential<br />To pump large molecules and clumps…<br />2 other processes:<br />Exocytosis<br />Endocytosis<br />The can change shape of membrane<br />
  39. 39. Types of Active transport<br />Molecular Transport<br />When small ions and molecules are carried across membrane<br />Endocytosis<br />Endo- means….<br />-Cyto- means…<br />-sis mean….<br />Exocytosis<br />Exo- means….<br />-Cyto- means…<br />-sis mean….<br />
  40. 40. Molecular Transport<br />Proteins are used to pump small molecules and ions across membrane even against the conc. Gradient<br />The cell devotes a lot of ENERGY to pumping things across membrane<br />Potassium, calcium, and sodium are some things that need to pumped across<br />
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  42. 42. Endocytosis<br />When cells need to take in large material<br />Process of taking material into the cell by process of infolding, or pockets, of the cell membrane<br />Pocket breaks loose from cell membrane and forms a vacuole or vesicle inside the cell<br />Two Types…<br />Phagocytosis<br />Pinocytosis<br />
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  44. 44. Two types of endocytosis:<br />1. Phagocytosis<br />“cell eating”<br />Extensions of cytoplasm surround the particle and package it within a food vacuole<br />Cell then engulfs the package<br />Amoebas<br />2. Pinocytosis<br />“cell drinking”<br />When cell needs to take up liquid<br />Tiny pockets in cell membrane form<br />Fill with liquid <br />Then pinch off to form vacuoles inside of cell<br />
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  47. 47. Exocytosis<br />Exo- means…<br />Cyto means…<br />Sis means…<br />When cell releases large amounts of material<br />Excretes stuff<br />Membrane of vacuole surrounding particle inside cell fuses with the cell membrane<br />The contents in vacuole are then forced out of the cell<br />We see this in removal of water by contractile vacuoles<br />
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  50. 50. MEMBRANE MAMBO!!!<br />