4.1  Cells Fig. 4.1  The size of cells and their contents 20 nm 20   m 20 mm 2 mm 0.2 mm 2   m 2 nm 0.2 nm 0.2   m
<ul><li>Robert Hooke (1665) </li></ul><ul><ul><li>Examined a thin slice of cork tissue </li></ul></ul><ul><ul><li>Observed...
<ul><li>In 1838 botanist Matthias Schleiden made a careful study of plant tissues and concluded that all plants “are aggre...
<ul><li>In its modern form, the cell theory includes three principles </li></ul>The Cell Theory  <ul><ul><li>1.  All organ...
<ul><li>Cells range in size from a few micrometers to several centimeters </li></ul><ul><li>Most cells are small because l...
Fig. 4.2  Surface-to-volume ratio
Visualizing Cells  <ul><li>Few cells can be see with the unaided eye </li></ul>Fig. 4.3  A scale of visibility
Visualizing Cells  <ul><li>We can’t see most cells because of the limited  resolution  of the human eye </li></ul><ul><ul>...
Light Microscopes  <ul><li>Use light as the illuminating source </li></ul> m  m
Light Microscopes  <ul><li>Use light as the illuminating source </li></ul> m  m
Electron Microscopes  <ul><li>Use a beam of electrons to produce the image </li></ul> m  m
3 different light microscopes Brightfield Darkfield Phase contrast
 
 
4.2  The Plasma Membrane <ul><li>Encases all living cells  </li></ul><ul><li>Its basic structure is represented by the  fl...
4.2  The Plasma Membrane <ul><li>In water, phospholipids spontaneously form a  bilayer </li></ul><ul><li>Cell membranes co...
<ul><li>Two main types </li></ul><ul><ul><li>Cell-surface proteins </li></ul></ul><ul><ul><ul><li>Project from the surface...
Fig. 4.6  Proteins are embedded within the lipid bilayer
4.3  Prokaryotic Cells <ul><li>There are two major kinds of cells </li></ul><ul><ul><li>Prokaryotes </li></ul></ul><ul><ul...
<ul><li>Prokaryotes have a very simple architecture </li></ul><ul><ul><li>They lack a nucleus and organelles </li></ul></u...
4.4  Eukaryotic Cells <ul><li>Appeared about 1.5 billion years ago </li></ul><ul><li>Include all cells alive today except ...
Fig. 4.10  Structure of a plant cell
Fig. 4.11  Structure of an animal cell
4.5  The Nucleus:  The Cell’s Control Center <ul><li>The  nucleus  is the command center of the cell </li></ul><ul><ul><li...
Passage for RNA and proteins  Site of assembly of ribosome subunits Fig. 4.12  The nucleus
4.6  The Endomembrane System <ul><li>An extensive system of interior membranes that divides the cell into compartments </l...
<ul><li>Internal membrane system creating channels and membrane-bound  vesicles </li></ul><ul><li>Consists of two distinct...
<ul><li>The ER transports the molecules it synthesizes to the Golgi complex </li></ul>Fig. 4.13  The endoplasmic reticulum
<ul><li>Golgi bodies  are flattened stack of membranes that are scattered throughout the cytoplasm </li></ul><ul><li>Depen...
Export material Import material Fig. 4.14  Golgi complex
<ul><li>Arise from the Golgi complex </li></ul><ul><li>They contain enzymes that break down macromolecules </li></ul><ul><...
<ul><li>Arise from the ER </li></ul><ul><li>They contain two sets of enzymes  </li></ul><ul><ul><li>One set is found in pl...
Fig. 4.15  How the endomembrane system works
4.7  Organelles That Contain DNA <ul><li>Two cell-like organelles contain DNA </li></ul><ul><ul><li>Mitochondria </li></ul...
<ul><li>Powerhouses of the cell </li></ul><ul><ul><li>Extract energy from organic molecules through  oxidative metabolism ...
Increase surface area Contains the mtDNA Fig. 4.16 a
Chloroplasts  <ul><li>Energy-capturing centers </li></ul><ul><ul><li>Sites of photosynthesis in plants and algae   </li></...
Stack of thylakoids Site of photosynthesis Fig. 4.17
The Endosymbiotic Theory  <ul><li>Proposes that mitochondria and chloroplasts arose by symbiosis from ancient bacteria   <...
Dr. Lynn Margulis and endosymbiont theory
Mitochondrial bacterial traits <ul><li>Capable of independent division </li></ul><ul><li>Circular chromosome with bacteria...
4.8  The Cytoskeleton:  Interior Framework of the Cell <ul><li>A dense network of protein fibers that  </li></ul><ul><ul><...
Made up of tubulin Make up microfilaments Fig. 4.19
Centrioles  <ul><li>Anchor and assemble microtubules   </li></ul><ul><li>May have originated as symbiotic bacteria </li></...
Cell Movement <ul><li>Essentially, all cell motion is tied to the movement of microfilaments and microtubules </li></ul><u...
Cell Movement <ul><li>Flagella and cilia </li></ul><ul><ul><li>Consist of a  9 + 2 arrangement  of microtubules </li></ul>...
Fig. 4.21 a  Eukaryotic flagellum
Moving Material Within the Cell <ul><li>Eukaryotic cells have developed high speed locomotives that run along microtubular...
Vacuoles <ul><li>In plants </li></ul><ul><ul><li>Store dissolved substances </li></ul></ul><ul><ul><li>Can increase the ce...
4.9  Outside the Plasma Membrane <ul><li>Cell Walls </li></ul><ul><ul><li>Offer protection and support </li></ul></ul><ul>...
4.9  Outside the Plasma Membrane <ul><li>Extracellular Matrix </li></ul><ul><ul><li>A mixture of  glycoproteins  secreted ...
4.10  Diffusion and Osmosis <ul><li>Diffusion  is the movement of molecules down their  concentration gradient </li></ul>E...
Osmosis  <ul><li>Diffusion of water through a semi-permeable membrane </li></ul><ul><li>Solutes   are substances dissolved...
Osmosis  Fig. 4.27
Osmosis  <ul><li>Movement of water into a cell creates  osmotic pressure </li></ul><ul><ul><li>This can cause a cell to sw...
Osmosis experiment with eggs <ul><li>First I put eggs in vinegar for a couple of days </li></ul>
<ul><li>This is what eggs look like without their shells </li></ul>Note that the eggs are already swollen—why is that?
<ul><li>Here you can see the semi-permeable membrane that will allow for passage of water and other small molecules, but n...
<ul><li>I put one egg in maple syrup and another one in a lime drink. </li></ul><ul><li>Egg on left started out at 91.0 g,...
<ul><li>I transferred the syrup egg to plain water and the lime-drink egg to 20% salt solution for 3 hours. </li></ul>Toni...
Final results of my experiment EGG #1 (syrup then water) EGG #2 (lime drink then salt water) After vinegar 91.0 g 75.7 g A...
4.11 Bulk Passage into and out of Cells <ul><li>Large amounts of material can be moved in and out of cells by membrane-bou...
Exocytosis  <ul><li>Means by which hormones, neurotransmitters and digestive enzymes are secreted in animal cells </li></u...
Endocytosis  <ul><li>Has three major forms </li></ul><ul><li>2.  Pinocytosis </li></ul><ul><ul><li>Engulfment of liquid ma...
<ul><ul><li>How low density lipoprotein (LDL) molecules bring cholesterol into animal cells  </li></ul></ul><ul><li>3.  Re...
4.12  Selective Permeability <ul><li>Cell membranes have  selective permeability </li></ul><ul><ul><li>They contain protei...
Facilitated Diffusion <ul><li>Net movement of a molecule down its concentration gradient facilitated by specific carrier p...
Facilitated Diffusion <ul><li>The rate can be saturated </li></ul><ul><ul><li>It increases up to a certain level and then ...
Active Transport <ul><li>The movement of molecules across a membrane against a concentration gradient </li></ul><ul><ul><l...
<ul><li>The Sodium-Potassium Pump </li></ul><ul><ul><li>Uses the energy of one ATP molecule to pump  3 Na +  outward and 2...
<ul><li>The Sodium-Potassium Pump </li></ul><ul><ul><li>Leads to fewer Na +  in the cell </li></ul></ul><ul><ul><li>This c...
Can enter against its concentration gradient Fig. 4.34  A coupled channel
Physiological and molecular genetic mechanisms of TTX resistance in the garter snake,  Thamnophis sirtalis Shana Geffeney ...
<ul><li>The rough skin newt </li></ul><ul><li>( Taricha granulosa ) </li></ul><ul><li>Extremely toxic and lethal to (almos...
Whole-animal resistance is measured using a locomotor performance bioassay. Expressed as 50% baseline performance after in...
The Geographic Mosaic of TTX Resistance <ul><li>Two apparent centers of elevated resistance - Central Oregon Coast and San...
<ul><li>The Proton Pump </li></ul>This process is termed  chemiosmosis <ul><ul><li>Expends metabolic energy to pump proton...
How Cells Get Information  <ul><li>Cells sense  chemical information  by means of cell surface  receptor proteins </li></u...
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Anat Cells

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Introduction to cells in general, size and shape of cells, the role of various organelles, prokaryotic versus eukaryotic cells

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Anat Cells

  1. 1. 4.1 Cells Fig. 4.1 The size of cells and their contents 20 nm 20  m 20 mm 2 mm 0.2 mm 2  m 2 nm 0.2 nm 0.2  m
  2. 2. <ul><li>Robert Hooke (1665) </li></ul><ul><ul><li>Examined a thin slice of cork tissue </li></ul></ul><ul><ul><li>Observed honeycombed compartments he called cellulae (L, small rooms) </li></ul></ul><ul><ul><ul><li>The term became cells </li></ul></ul></ul><ul><li>Matthias Schleiden and Theodor Schwann </li></ul><ul><ul><li>Proposed the first two statements of the cell theory in 1838-39 (2 centuries later!) </li></ul></ul>The Cell Theory
  3. 3. <ul><li>In 1838 botanist Matthias Schleiden made a careful study of plant tissues and concluded that all plants “are aggregates of fully individualized, independent separate beings, namely the cells themselves.” </li></ul><ul><li>In 1839 Theodor Schwann made similar conclusions about animal tissues. </li></ul>
  4. 4. <ul><li>In its modern form, the cell theory includes three principles </li></ul>The Cell Theory <ul><ul><li>1. All organisms are composed of one or more cells </li></ul></ul><ul><ul><li>2. Cells are the smallest living things </li></ul></ul><ul><ul><li>3. Cells arise only by division of a previously existing cell </li></ul></ul>
  5. 5. <ul><li>Cells range in size from a few micrometers to several centimeters </li></ul><ul><li>Most cells are small because larger cells do not function efficiently </li></ul><ul><li>It is advantageous to have a large surface-to-volume ratio </li></ul><ul><ul><li>As cell size increases, volume grows much faster than surface area </li></ul></ul>Cell Size
  6. 6. Fig. 4.2 Surface-to-volume ratio
  7. 7. Visualizing Cells <ul><li>Few cells can be see with the unaided eye </li></ul>Fig. 4.3 A scale of visibility
  8. 8. Visualizing Cells <ul><li>We can’t see most cells because of the limited resolution of the human eye </li></ul><ul><ul><li>Resolution is the minimum distance two points can be apart and still be seen as two points </li></ul></ul><ul><ul><li>Resolution of the human eye is 100  </li></ul></ul><ul><li>One way to increase resolution is to increase magnification, using microscopes </li></ul><ul><li>There are two main types of microscopes </li></ul>
  9. 9. Light Microscopes <ul><li>Use light as the illuminating source </li></ul> m  m
  10. 10. Light Microscopes <ul><li>Use light as the illuminating source </li></ul> m  m
  11. 11. Electron Microscopes <ul><li>Use a beam of electrons to produce the image </li></ul> m  m
  12. 12. 3 different light microscopes Brightfield Darkfield Phase contrast
  13. 15. 4.2 The Plasma Membrane <ul><li>Encases all living cells </li></ul><ul><li>Its basic structure is represented by the fluid-mosaic model </li></ul><ul><ul><li>Phospholipid bilayer with embedded proteins </li></ul></ul>Fig. 4.4 Phospholipid structure
  14. 16. 4.2 The Plasma Membrane <ul><li>In water, phospholipids spontaneously form a bilayer </li></ul><ul><li>Cell membranes contain zones called lipid rafts </li></ul><ul><ul><li>Heavily enriched in cholesterol </li></ul></ul>Fig. 4.5
  15. 17. <ul><li>Two main types </li></ul><ul><ul><li>Cell-surface proteins </li></ul></ul><ul><ul><ul><li>Project from the surface of the membrane </li></ul></ul></ul><ul><ul><ul><li>Act as markers or receptors </li></ul></ul></ul><ul><ul><li>Transmembrane proteins </li></ul></ul><ul><ul><ul><li>Extend all the way across the bilayer </li></ul></ul></ul><ul><ul><ul><li>Provide channels in and out of the cell </li></ul></ul></ul>Proteins Within the Membrane
  16. 18. Fig. 4.6 Proteins are embedded within the lipid bilayer
  17. 19. 4.3 Prokaryotic Cells <ul><li>There are two major kinds of cells </li></ul><ul><ul><li>Prokaryotes </li></ul></ul><ul><ul><li>Eukaryotes </li></ul></ul><ul><li>Prokaryotes include bacteria and archaea </li></ul><ul><ul><li>Over 5,000 species are recognized </li></ul></ul><ul><li>Prokaryotes come in three main shapes </li></ul>Fig. 4.9 Rod Spherical Spiral
  18. 20. <ul><li>Prokaryotes have a very simple architecture </li></ul><ul><ul><li>They lack a nucleus and organelles </li></ul></ul>Pilus Fig. 4.8 Found in all prokaryotes
  19. 21. 4.4 Eukaryotic Cells <ul><li>Appeared about 1.5 billion years ago </li></ul><ul><li>Include all cells alive today except bacteria and archaea </li></ul><ul><li>Are larger than prokaryotic cells </li></ul><ul><li>Have a much more complex architecture </li></ul><ul><ul><li>Possess nucleus and a variety of organelles </li></ul></ul>
  20. 22. Fig. 4.10 Structure of a plant cell
  21. 23. Fig. 4.11 Structure of an animal cell
  22. 24. 4.5 The Nucleus: The Cell’s Control Center <ul><li>The nucleus is the command center of the cell </li></ul><ul><ul><li>It directs all of its activities </li></ul></ul><ul><li>It also stores the cell’s hereditary information </li></ul><ul><ul><li>The DNA is associated with proteins </li></ul></ul><ul><ul><li>During cell division, it condenses into chromosomes </li></ul></ul><ul><ul><li>After cell division, it relaxes to form chromatin </li></ul></ul>
  23. 25. Passage for RNA and proteins Site of assembly of ribosome subunits Fig. 4.12 The nucleus
  24. 26. 4.6 The Endomembrane System <ul><li>An extensive system of interior membranes that divides the cell into compartments </li></ul><ul><li>It consists of </li></ul><ul><ul><li>Endoplasmic reticulum </li></ul></ul><ul><ul><li>Golgi complex </li></ul></ul><ul><ul><li>Lysosomes </li></ul></ul><ul><ul><li>Peroxisomes </li></ul></ul>
  25. 27. <ul><li>Internal membrane system creating channels and membrane-bound vesicles </li></ul><ul><li>Consists of two distinct regions </li></ul><ul><ul><li>Rough ER </li></ul></ul><ul><ul><ul><li>Studded with ribosomes </li></ul></ul></ul><ul><ul><ul><li>Involved in protein synthesis </li></ul></ul></ul><ul><ul><li>Smooth ER </li></ul></ul><ul><ul><ul><li>Embedded with enzymes </li></ul></ul></ul><ul><ul><ul><li>Involved in lipid and carbohydrate synthesis </li></ul></ul></ul>Endoplasmic Reticulum (ER)
  26. 28. <ul><li>The ER transports the molecules it synthesizes to the Golgi complex </li></ul>Fig. 4.13 The endoplasmic reticulum
  27. 29. <ul><li>Golgi bodies are flattened stack of membranes that are scattered throughout the cytoplasm </li></ul><ul><li>Depending on the cell, the number of Golgi bodies ranges from a few to several hundred </li></ul><ul><ul><li>These are collectively referred to as the Golgi complex </li></ul></ul><ul><li>The Golgi complex collects, packages, modifes and distributes molecules </li></ul>The Golgi Complex
  28. 30. Export material Import material Fig. 4.14 Golgi complex
  29. 31. <ul><li>Arise from the Golgi complex </li></ul><ul><li>They contain enzymes that break down macromolecules </li></ul><ul><li>Function in intracellular digestion of </li></ul><ul><ul><li>Worn-out cellular components </li></ul></ul><ul><ul><li>Substances taken into cells </li></ul></ul><ul><ul><li>The resulting material is then recycled </li></ul></ul>Lysosomes
  30. 32. <ul><li>Arise from the ER </li></ul><ul><li>They contain two sets of enzymes </li></ul><ul><ul><li>One set is found in plants </li></ul></ul><ul><ul><ul><li>Converts fats to sugars </li></ul></ul></ul><ul><ul><li>The other set is found in animals </li></ul></ul><ul><ul><ul><li>Detoxifies various harmful molecules </li></ul></ul></ul>Peroxisomes
  31. 33. Fig. 4.15 How the endomembrane system works
  32. 34. 4.7 Organelles That Contain DNA <ul><li>Two cell-like organelles contain DNA </li></ul><ul><ul><li>Mitochondria </li></ul></ul><ul><ul><ul><li>Found in almost all eukaryotes </li></ul></ul></ul><ul><ul><li>Chloroplasts </li></ul></ul><ul><ul><ul><li>Found only in plants and algae </li></ul></ul></ul>
  33. 35. <ul><li>Powerhouses of the cell </li></ul><ul><ul><li>Extract energy from organic molecules through oxidative metabolism </li></ul></ul>Mitochondria <ul><li>Sausage-shaped organelles, about the size of a bacterial cell </li></ul><ul><li>Like bacteria, they </li></ul><ul><ul><li>1. Possess circular DNA </li></ul></ul><ul><ul><li>2. Divide by simple fission </li></ul></ul>Fig. 4.16 b
  34. 36. Increase surface area Contains the mtDNA Fig. 4.16 a
  35. 37. Chloroplasts <ul><li>Energy-capturing centers </li></ul><ul><ul><li>Sites of photosynthesis in plants and algae </li></ul></ul><ul><li>Like bacteria, they </li></ul><ul><ul><li>1. Possess circular DNA </li></ul></ul><ul><ul><li>2. Divide by simple fission </li></ul></ul><ul><li>Like mitochondria, they are surrounded by two membranes </li></ul><ul><ul><li>However, inner membrane much more complex </li></ul></ul>
  36. 38. Stack of thylakoids Site of photosynthesis Fig. 4.17
  37. 39. The Endosymbiotic Theory <ul><li>Proposes that mitochondria and chloroplasts arose by symbiosis from ancient bacteria </li></ul><ul><li>This theory is supported by a wealth of evidence </li></ul>Fig. 4.18
  38. 40. Dr. Lynn Margulis and endosymbiont theory
  39. 41. Mitochondrial bacterial traits <ul><li>Capable of independent division </li></ul><ul><li>Circular chromosome with bacterial DNA sequences </li></ul><ul><li>Procaryotic ribosomes </li></ul><ul><li>Inhibited by drugs that affect bacterial membranes </li></ul><ul><li>Side note: mtDNA inherited maternally </li></ul>
  40. 42. 4.8 The Cytoskeleton: Interior Framework of the Cell <ul><li>A dense network of protein fibers that </li></ul><ul><ul><li>1. Supports the shape of the cell </li></ul></ul><ul><ul><li>2. Anchors organelles </li></ul></ul><ul><li>Three different kinds of protein fibers </li></ul><ul><ul><li>Microfilaments </li></ul></ul><ul><ul><li>Microtubules </li></ul></ul><ul><ul><li>Intermediate filaments </li></ul></ul>
  41. 43. Made up of tubulin Make up microfilaments Fig. 4.19
  42. 44. Centrioles <ul><li>Anchor and assemble microtubules </li></ul><ul><li>May have originated as symbiotic bacteria </li></ul><ul><li>Not found in higher plants and fungi </li></ul>Fig. 4.20
  43. 45. Cell Movement <ul><li>Essentially, all cell motion is tied to the movement of microfilaments and microtubules </li></ul><ul><li>Changes in the shape of microfilaments </li></ul><ul><ul><li>Enable some cells to change shape quickly </li></ul></ul><ul><ul><li>Allow some cells to crawl </li></ul></ul><ul><ul><li>Cause animal cells to divide </li></ul></ul>
  44. 46. Cell Movement <ul><li>Flagella and cilia </li></ul><ul><ul><li>Consist of a 9 + 2 arrangement of microtubules </li></ul></ul><ul><ul><li>Anchored in the cell by a basal body </li></ul></ul><ul><li>Flagella </li></ul><ul><ul><li>Long and few in number </li></ul></ul><ul><li>Cilia </li></ul><ul><ul><li>Short and numerous </li></ul></ul>Fig. 4.21 b Cilia Paramecium
  45. 47. Fig. 4.21 a Eukaryotic flagellum
  46. 48. Moving Material Within the Cell <ul><li>Eukaryotic cells have developed high speed locomotives that run along microtubular tracks </li></ul><ul><li>Kinesin </li></ul><ul><ul><li>Motor protein that moves vesicles to the cell’s periphery </li></ul></ul><ul><li>Dynein </li></ul><ul><ul><li>Motor protein that moves vesicles to the cell’s interior </li></ul></ul>Fig. 4.22
  47. 49. Vacuoles <ul><li>In plants </li></ul><ul><ul><li>Store dissolved substances </li></ul></ul><ul><ul><li>Can increase the cell’s surface area </li></ul></ul><ul><li>In protists </li></ul><ul><ul><li>Contractile vacuoles are used to pump excess water </li></ul></ul>Fig. 4.23
  48. 50. 4.9 Outside the Plasma Membrane <ul><li>Cell Walls </li></ul><ul><ul><li>Offer protection and support </li></ul></ul><ul><ul><li>Fungal cell walls are made up of chitin </li></ul></ul><ul><ul><li>Plant cell walls are made up of cellulose </li></ul></ul>Glues cells together Fig. 4.24
  49. 51. 4.9 Outside the Plasma Membrane <ul><li>Extracellular Matrix </li></ul><ul><ul><li>A mixture of glycoproteins secreted by animal cells </li></ul></ul>Links ECM to the cytoskeleton <ul><ul><li>Helps coordinate the behavior of all cells in a tissue </li></ul></ul>Fig. 4.25
  50. 52. 4.10 Diffusion and Osmosis <ul><li>Diffusion is the movement of molecules down their concentration gradient </li></ul>Equilibrium Fig. 4.26
  51. 53. Osmosis <ul><li>Diffusion of water through a semi-permeable membrane </li></ul><ul><li>Solutes are substances dissolved in a solution </li></ul><ul><ul><li>Hyperosmotic solution contains higher concentration of solutes than the cell </li></ul></ul><ul><ul><li>Hypoosmotic solution contains lower concentration of solutes than the cell </li></ul></ul><ul><ul><li>Isotonic solution contains equal concentration of solutes as the cell </li></ul></ul>
  52. 54. Osmosis Fig. 4.27
  53. 55. Osmosis <ul><li>Movement of water into a cell creates osmotic pressure </li></ul><ul><ul><li>This can cause a cell to swell and burst </li></ul></ul>Normal shape Shape in pure water Fig. 4.28 Osmotic pressure in a red blood cell
  54. 56. Osmosis experiment with eggs <ul><li>First I put eggs in vinegar for a couple of days </li></ul>
  55. 57. <ul><li>This is what eggs look like without their shells </li></ul>Note that the eggs are already swollen—why is that?
  56. 58. <ul><li>Here you can see the semi-permeable membrane that will allow for passage of water and other small molecules, but not allow proteins and large molecules to pass </li></ul>
  57. 59. <ul><li>I put one egg in maple syrup and another one in a lime drink. </li></ul><ul><li>Egg on left started out at 91.0 g, and after the syrup treatment weighed 47.4 g. Egg on right was 75.7 g and went to 79.8 g. </li></ul>Tell me about the tonicity of the syrup and lime drink relative to the inside of the egg
  58. 60. <ul><li>I transferred the syrup egg to plain water and the lime-drink egg to 20% salt solution for 3 hours. </li></ul>Tonicity?
  59. 61. Final results of my experiment EGG #1 (syrup then water) EGG #2 (lime drink then salt water) After vinegar 91.0 g 75.7 g After treatment #1 47.4 g 79.8 g After treatment #2 ?? (lysis) 79.6
  60. 62. 4.11 Bulk Passage into and out of Cells <ul><li>Large amounts of material can be moved in and out of cells by membrane-bound vesicles </li></ul><ul><li>Exocytosis </li></ul><ul><ul><li>Discharge of material from vesicles at the cell surface </li></ul></ul><ul><li>Endocytosis </li></ul><ul><ul><li>The plasma membrane envelops particles and brings them into the cell interior </li></ul></ul>
  61. 63. Exocytosis <ul><li>Means by which hormones, neurotransmitters and digestive enzymes are secreted in animal cells </li></ul>Fig. 4.30
  62. 64. Endocytosis <ul><li>Has three major forms </li></ul><ul><li>2. Pinocytosis </li></ul><ul><ul><li>Engulfment of liquid material </li></ul></ul><ul><li>1. Phagocytosis </li></ul><ul><ul><li>Engulfment of particulate material </li></ul></ul>Fig. 4.29 a Fig. 4.29 b
  63. 65. <ul><ul><li>How low density lipoprotein (LDL) molecules bring cholesterol into animal cells </li></ul></ul><ul><li>3. Receptor-Mediated Endocytosis </li></ul><ul><ul><li>The process is highly specific and very fast </li></ul></ul>Fig. 4.31
  64. 66. 4.12 Selective Permeability <ul><li>Cell membranes have selective permeability </li></ul><ul><ul><li>They contain protein channels that allow only certain molecules to pass </li></ul></ul><ul><li>Selective Diffusion </li></ul><ul><ul><li>Allows molecules to pass through open channels in either direction </li></ul></ul><ul><ul><li>Ion channels </li></ul></ul><ul><ul><ul><li>If the ion fits the pore, it goes through </li></ul></ul></ul>
  65. 67. Facilitated Diffusion <ul><li>Net movement of a molecule down its concentration gradient facilitated by specific carrier proteins </li></ul>Fig. 4.32
  66. 68. Facilitated Diffusion <ul><li>The rate can be saturated </li></ul><ul><ul><li>It increases up to a certain level and then levels off </li></ul></ul>Fig. 4.32
  67. 69. Active Transport <ul><li>The movement of molecules across a membrane against a concentration gradient </li></ul><ul><ul><li>This is possible by the expenditure of energy </li></ul></ul><ul><li>Two types of channels are mainly used </li></ul><ul><ul><li>1. Sodium-Potassium Pump </li></ul></ul><ul><ul><li>2. Proton Pump </li></ul></ul>
  68. 70. <ul><li>The Sodium-Potassium Pump </li></ul><ul><ul><li>Uses the energy of one ATP molecule to pump 3 Na + outward and 2 K + into the cell </li></ul></ul>Fig. 4.33
  69. 71. <ul><li>The Sodium-Potassium Pump </li></ul><ul><ul><li>Leads to fewer Na + in the cell </li></ul></ul><ul><ul><li>This concentration gradient is exploited in many ways, including </li></ul></ul><ul><ul><ul><li>1. The conduction of signals along nerve cells </li></ul></ul></ul><ul><ul><ul><ul><li>Chapter 28 </li></ul></ul></ul></ul><ul><ul><ul><li>2. The transport of material into the cell against their concentration gradient </li></ul></ul></ul><ul><ul><ul><ul><li>Coupled channels </li></ul></ul></ul></ul>
  70. 72. Can enter against its concentration gradient Fig. 4.34 A coupled channel
  71. 73. Physiological and molecular genetic mechanisms of TTX resistance in the garter snake, Thamnophis sirtalis Shana Geffeney Department of Biology Utah State University
  72. 74. <ul><li>The rough skin newt </li></ul><ul><li>( Taricha granulosa ) </li></ul><ul><li>Extremely toxic and lethal to (almost) all predators. </li></ul><ul><li>A single newt can have up to 14 mg of tetrodotoxin (TTX) in its skin. </li></ul><ul><li>Toxicity varies geographically. </li></ul>
  73. 75. Whole-animal resistance is measured using a locomotor performance bioassay. Expressed as 50% baseline performance after injection with TTX. Whole-Animal TTX Resistance TTX Dose (MAMU) Resistance (% Crawl Speed) 1 0.1 10 100 1000 10000 100 0 20 40 60 80 > 100 MAMU 35-100 25-35 15-25 10-15 5-10 4-5 <4 San Mateo, CA Benton, OR Gilroy, CA Bear Lake, ID Inland Lake, BC
  74. 76. The Geographic Mosaic of TTX Resistance <ul><li>Two apparent centers of elevated resistance - Central Oregon Coast and San Francisco Bay Area </li></ul><ul><li>At least two independent origins of elevated TTX resistance within T. sirtalis. </li></ul>(Brodie et al., 2002)
  75. 77. <ul><li>The Proton Pump </li></ul>This process is termed chemiosmosis <ul><ul><li>Expends metabolic energy to pump protons across membranes </li></ul></ul>Fig. 4.35
  76. 78. How Cells Get Information <ul><li>Cells sense chemical information by means of cell surface receptor proteins </li></ul><ul><ul><li>These bind specific molecules and transmit information to the cell </li></ul></ul><ul><li>Cells sense electrical information by means of voltage-sensitive channels </li></ul><ul><ul><li>These allow ions into or out of the cell in response to electric signals </li></ul></ul>

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