Cell Membrane

1. The Cell MembraneWhat do you notice about the picture below?What parts can you name? Do you know their functions?

2. Cell Membrane 8,000 membranes to equal one sheet of paper

3. Functions of Cell Membrane • Control what enters and exits the cell • Help cell keep its shape • Recognize substances that might harm the cell. • Communicate with other cells

4. Cell membrane separates living cell from nonliving surroundings • Controls traffic in & out of the cell • Selectively permeable - allows some substances to cross more easily than others. • WHY? Hydrophobic tails vs hydrophilic heads

5. What has to get in and out of the cell? • Oxygen CO2 • Glucose Waste • Amino acid new proteins • Vitamins • water

6. Parts of the Cell Membrane • Phospholipids 3. Proteins • Cholesterol 4. Carbohydrates

7. Phospholipids Phosphate 1. Fatty acid tails • hydrophobic 2. Phosphate group 3. Glycerol • Hydrophilic Fatty acid Aaaah, one of thosestructure–function examples

8. Why are the phosolipids arrange this way? • Heads - hydrophilic face outward • Tails - Hydrophobic face inward • Water surrounds the cell and is inside the cell. Hydrophilic must face outward. • Arranged as a bilayer

9. The Arrangement of the Phosolipids determine how particles pass through the cell membrane? • If a particle is small and not charged then it can move straight through the membrane. • If the particle is large and charged, then it has to move through the cell proteins. • Aquaporins - protein channel that water moves through.

10. 3 Functions of Proteins – read page 10 • Pumps material through the membrane - large and charged particles channels (pumps) 2. Proteins on the inside of cell. Attach to cytoskeleton. Help with structure!! 3. Receptors – Carbo. Are attached to proteins! 4. Enzymes!

11. Membrane carbohydrates • Play a key role in cell-cell recognition • ability of a cell to distinguish one cell from another • antigens • important in organ & tissue development • basis for rejection of foreign cells by immune system

12. Function of Cholesterol • Strengthen cell membrane – phosolipids are not bonded so membrane is not strong!

13. Fluid Mosaic Model Describes the characteristics of the cell membrane • Cell membrane is flexible not rigid. Acts as a fluid. • Cell membrane is constructed for many different parts.

14. Selective Permeability • Cell membrane allows some materials in and others not. • Homeostasis: Cell maintenance of stable internal conditions in a changing environment. • How a molecules moves across a membrane depends on the size, polarity, and concentration of the molecules.

15. Molecules are constantly moving!! • You must understand that molecules are constantly moving. • The more energy added the faster they move. • Move from an area of a higher concentration to an area of lower concentration.

16. Video molecular movement!!!!! • Air freshener!!! Perfume!!! Farts!!!!! • Do you Agree that Molecules Must Move Across Membrane?

17. Concentration Gradient • The difference in the concentration of molecules in two different regions. • Can be a room or a cell!!!! • Equilibrium: molecules will continue to move until equal on both sides.

18. 3 Ways Particles Move!! 1.Small and non charged particles can just move through the membrane. 2. Small polar molecules move through the protein channels. 3. Large particles move in vesciles.

19. Animations of Active Transport & Passive Transport Weeee!!! high low This is gonna be hard work!! high low Types of Cellular Transport • Passive Transport cell doesn’t use energy • Diffusion • Facilitated Diffusion • Osmosis • Active Transport cell does use energy • Protein Pumps • Endocytosis • Exocytosis

20. Transport summary simplediffusion facilitateddiffusion ATP activetransport

21. 3 Types of Passive Transport • Diffusion • Facilitative Diffusion – diffusion with the help of transport proteins • Osmosis – diffusion of water through aquaporin.

22. Passive Transport 1. cell uses no energy 2. molecules move randomly 3. Molecules spread out from an area of high concentration to an area of low concentration. • (HighLow) • CAN BE THROUGH A CHANNEL!!!

23. Simple Diffusion Animation Passive Transport:1. Diffusion • Diffusion: random movement of particles from an area of high concentration to an area of low concentration. (High to Low) • Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-Note: molecules will still move around but stay spread out. http://bio.winona.edu/berg/Free.htm

24. Diffusion • Move from HIGH to LOW concentration • “passive transport” • no energy needed • Small and non charged • Straight through membrane movement of water diffusion osmosis

25. inside cell outside cell Diffusion through phospholipid bilayer • What molecules can get through directly? • fats & other lipids • What molecules can NOT get through directly? • polar molecules • H2O • ions • salts, ammonia • large molecules • starches, proteins lipid salt NH3 sugar aa H2O

26. Passive Transport: Facilitated Diffusion A B 2. Facilitated diffusion: diffusion of specific particles through transport proteins found in the membrane • Transport Proteins are specific – they “select” only certain molecules to cross the membrane • Transports larger or charged molecules Facilitated diffusion(Channel Protein) Diffusion (Lipid Bilayer) Carrier Protein • http://bio.winona.edu/berg/Free.htm

27. high low Facilitated Diffusion • Diffusion through protein channels • channels move specific molecules across cell membrane • no energy needed facilitated = with help open channel = fast transport “The Bouncer”

28. Passive Transport: Facilitated Diffusion Glucose molecules Cellular Transport From a- High High Concentration • Channel Proteins animations Cell Membrane Protein channel Low Concentration Low Transport Protein Through a  Go to Section:

29. Passive Transport: 3. Osmosis Osmosis animation • 3.Osmosis: facilitated diffusion of water through a selectively permeable membrane • Water moves from high to low concentrations • AQUAPORIN • Water moves freely through pores. • Solute (green) to large to move across.

30. Effects of Osmosis on Life • Osmosis- diffusion of water through a selectively permeable membrane • Water is so small and there is so much of it the cell can’t control it’s movement through the cell membrane.

31. hypotonic hypertonic Concentration of water • Direction of osmosis is determined by the amount of solution in the cell. If there is more solute then less water! • Hypertonic - more solute, less water • Hypotonic - less solute, more water • Isotonic - equal solute, equal water water net movement of water

32. 3 Types of Solutions For a Cell 1. Hypertonic - more solute, less water. More water inside cell; it leaves 2. Hypotonic - less solute, more water. More water outside cell; water enters 3. Isotonic - equal solute, equal water Equal – net movement equal!

33. Managing water balance • Cell survival depends on balancing water uptake & loss freshwater balanced saltwater

34. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypotonic Solution Hypotonic: The solution has a lower concentration of solutes and a higher concentration of water than inside the cell. (Low solute; High water) Result: Water moves from the solution to inside the cell): Cell Swells and bursts open (cytolysis)!

35. Managing water balance • Hypotonic • a cell in fresh water • example: Paramecium • problem: gains water,swells & can burst • water continually enters Paramecium cell • solution: contractile vacuole • pumps water out of cell • ATP • plant cells • turgid ATP freshwater

36. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Hypertonic Solution Hypertonic: The solution has a higher concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water) shrinks Result: Water moves from inside the cell into the solution: Cell shrinks (Plasmolysis)!

37. Managing water balance • Hypertonic • a cell in salt water • example: shellfish • problem: lose water & die • solution: take up water or pump out salt • plant cells • plasmolysis = wilt saltwater

38. Osmosis Animations for isotonic, hypertonic, and hypotonic solutions Isotonic Solution Isotonic: The concentration of solutes in the solution is equal to the concentration of solutes inside the cell. Result: Water moves equally in both directions and the cell remains same size! (Dynamic Equilibrium)

39. Managing water balance • Isotonic • animal cell immersed in mild salt solution • example: blood cells in blood plasma • problem: none • no net movement of water • flows across membrane equally, in both directions • volume of cell is stable balanced

40. What type of solution are these cells in? B C A Hypertonic Isotonic Hypotonic

41. low high Active Transport • Cells may need to move molecules againstconcentration gradient • shape change transports solute from one side of membrane to other • protein “pump” • “costs” energy = ATP conformationalchange ATP “The Doorman”

42. Active Transport • 1. cell uses energy • 2. actively moves molecules to where they are needed • 3. Movement from an area of low concentration to an area of high concentration • AGAINST THE CONCENTRATION GRADIENT! • (Low  High)

43. How Organisms Deal with Osmotic Pressure • Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called tugor pressure. • A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding. • Salt water fish pump salt out of their specialized gills so they do not dehydrate. • Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water. • Paramecium (protist) removing excess water video

44. Aquaporins 1991 | 2003 • Water moves rapidly into & out of cells • evidence that there were water channels Peter Agre John Hopkins Roderick MacKinnon Rockefeller

45. Sodium Potassium Pumps (Active Transport using proteins) Types of Active Transport • 1. Protein Pumps -transport proteins that require energy to do work • Example: Sodium / Potassium Pumps are important in nerve responses. Protein changes shape to move molecules: this requires energy!

46. Types of Active Transport • 2.Endocytosis: taking bulky material into a cell • Uses energy • Cell membrane in-folds around food particle • “cell eating” • forms food vacuole & digests food • This is how white blood cells eat bacteria!

47. Endocytosis fuse with lysosome for digestion phagocytosis pinocytosis non-specificprocess triggered bymolecular signal receptor-mediated endocytosis

48. How about large molecules? • Moving large molecules into & out of cell • through vesicles & vacuoles • endocytosis • phagocytosis = “cellular eating” • pinocytosis = “cellular drinking” • exocytosis exocytosis

49. Types of Active Transport Endocytosis & Exocytosis animations 3. Exocytosis:Forces material out of cell in bulk • membrane surrounding the material fuses with cell membrane • Cell changes shape – requires energy • EX: Hormones or wastes released from cell