The Cell Membrane and Cell Function

The Cell Membrane and Cell Function

BIO 111

Ch 5 6th Ed

  1. The Cell Membrane and Cell Function
  2. Cell membrane recognize self
  3. Organ rejection
  4. Name tags of proteins, carbs and lipids
  5. cytoskeleton
  6. cell’s interior scaffolding
  7. protein fibers
  8. cytoskeleton + cell membrane
  9. cells framework
  10. organizes interior of cell
  11. distinguishes one cell from another
  12. The Structure of a Cell Membrane
  13. Lipid molecules attached to phosphates groups
  14. Phospholipids – hydrophilic
  15. Lipid end – hydrophobic
  16. Phospholipids bilayer – sandwich-like layering repels both charged and uncharged particles
  17. Proteins- embedded
  18. Passageway for water soluable molecules and ions
  19. Also act as carriers
  20. fluid mosaic – everything moves within the layer
  21. receptors – glycoproteins on or within the membrane surface
  22. ratios of proteins to phospholipids reflect health. Upset = sickness
  23. multiple sclerosis – not enough fat in cell membranes (cells that are supposed to create mylin
  24. TaySachs – EXCESS lipid in cell membrane (cells that build TOO MUCH mylin)
  25. Diffusion: Passive Flow Across a Membrane
  • Acqueous solution – homogeneous mixture of solute + solvent (water)
  • Concentration- how much solute is in the solvent
  • Diffusion moves substances from high to low concentration
  • Membranes are selectively permeable
  • Oxygen, water and carbon dioxide freely cross membranes by diffusion
  • Heat increases rate of diffusion
  • Concentration gradient- differences in concentration from low to high or vice-versa
  • other types of gradients:
  • ph
  • electrical
  • pressure
  • ions
  • dynamic equilibrium
  • equal movement back and forth
  • Osmosis is the movement of water
  • Same as diffusion, but across a membrane
  • Controlled by solute concentration inside and outside the cell
  • Solutes can’t move, so water does
  • Tonicity
  • isotonic – solutes inside and outside have the same concentration
  • hypotonic – hypertonic
  • relative terms
  • can refer to inside or outside of cell
  • Red blood cell example – pg 70
  • Contractile vacuole – organ that regulates water movement in single cell critters.
  • Turgor pressure – how plant cells regulate how much water can flow into cell – water forced against the cell wall
  1. Transport Proteins
  2. Channels Allow Passive Movement at a faster Rate
  3. Forms an opening (tube) for solutes to pass through
  4. Charge and size regulate what passes
  5. FAST – 100 million ions or molecules/second
  6. Form of facilitated diffusion
  7. Carriers move cargo from one side to the other
  8. Carrier protein binds to ion or molecule
  9. Protein changes shape the forces particle to other side of membrane
  10. Can be passive (no ATP- therefore another facilitated diffusion) or active (use ATP)
  11. passive facilited 100-1000/second
  12. active – can move against the gradient
  13. Pumps use energy to move molecules or ions against a gradient
  14. Sodium-potassium pump – see animation
  15. Cotransport
  16. see diagram (figure 5.11) pg 72
  17. creates gradient
  18. gradient used to transport substance
  19. symporter molecule responds to gradient movement
  20. Vesicles perform mass movements by packaging substances
  21. Exocytosis- fluids and large particles out of cell
  22. Ex – sperm – releases enzymes that penetrate egg
  23. Endocytosis- capture large molecules and fluid on surface and moves into cell
  24. pinocytosis – just water or solutes and water
  25. phagocytosis – captures and destroys debris, small organisms, bacteria
  26. endosome – phagocytic vesicle fuses with a lysosome
  27. receptor mediated endocytosis
  28. receptor protein binds to ligand, membrane indents, pulling ligand into the cell
  29. Ex. Liver cells take in cholesterol this way
  30. Trancytosis- combination of endo and exocytosis
  31. moves particles from one side of the cell to another
  32. The Cytoskeleton
  33. Tubules and filaments guide organelle movement, provide shape and link molecules
  34. Compare micro tubules, aned both filament – Figure 5.14 pg 75
  35. Microtubules are composed of tubulin
  36. Composed of:tubulin – protein dimmers (pairs)
  37. Length adjustable - + or – molecules of tubulin
  38. Number and arrangement changes based on cell cycle (spindles)
  39. Cancer treatments – some effect tubule assembly
  40. Another function: locomotion
  41. cilia
  42. 9 microtubule pairs around a central pair (9+2) pattern
  43. Dynein – connects inner and outer proteins (wheel-like) 5.16 pg 76
  44. Bad dynein arrangement leads to disease
  45. Wave-like motion
  46. Clean respiratory track, move egg down fallopian tube, single celled critters swim
  47. flagella
  48. 9+2 arrangement but longer
  49. Whiplike – propulsion
  50. Sperm cells – humans 1, cycad tree thousands
  51. Another function: trackway in cell
  52. moves organelles and proteins within
  53. squid color changes – rearrange pigment
  54. Microfilaments are composed of actin
  55. Long rod of protein actin
  56. Not hollow
  57. Smaller than microtubules
  58. Function:
  59. strength to cell (withstand stretching and bending)
  60. anchor cells together
  61. muscle contractions
  62. actin and myosin interact in a sliding filament
  63. Intermediate filaments provide scaffolding
  64. Size – between previous two
  65. Made of many different proteins
  66. Dimmers intwined into coiled rods
  67. Abundant in skin cells and nerve cells
  68. Maintain cell’s shape
  69. Inner framework of cell
  70. Epidermolysis bullosa
  71. intermediate filaments abnormal – skin blisters easily
  72. Cell Signaling and Response
  73. Cell to cell communication
  74. Animal cell junction types depend on function (see figure5.19 pg 80)
  75. Tight junction
  76. membranes fuse cells at a single point (like belt)
  77. create sheets-
  78. like in human digestive tract
  79. blood vessels (capillaries) in brain (400 mile-blood brain barrier)
  80. lipids chemicals soluble – heroin, valium, nicotine, cocaine alcohol
  81. oxygen passes
  82. water soluble – different pathways
  83. desmosome
  84. links intermediate filaments in adjacent cells
  85. hold skin cells in place (cell to extracellular matrix)
  86. gap junction
  87. links cytoplasm fo adjacent cells (ion exchange)
  88. heart muscle cells
  89. muscle cells in digestive track
  90. Cell Walls Add structure and allow interaction
  91. Around cells of bacteria, arhaea, fungi, algae and plants
  92. Provide chape and volume AND interact
  93. Composition depends on function of cell, surrounding or life cycle of cell
  94. Plants – mostly cellulose and pectin (like glue)
  95. CW is layers. Oldest layer is most outside layer
  96. where cell walls meet: middle lamella
  97. plasmodesmata – link plant cells (tunnels to cells)
  98. Cellular Adhesion directs cell movement
  99. Adhesion – cells stick together
  100. Cellular Adhesion molecules (CAM’s) (SEE pg 82 Figure 5.21)
  101. help guide white blood cells to inflammation site
  102. Know sequence
  103. Signal Transduction mediates messages
  104. Signal Transduction – how cells get “messages” from outside the cell
  105. NO and cyclic AMP (cAMP) used in plants, fungi and animal
  106. cell membrane interacts with chemicals
  107. figure 5.22 pg 83
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