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Chapters 6 and 7

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  • Chapt6and7

    1. 1. <ul><li>Chapter 6 </li></ul><ul><li>Cell Structure: A Tour of the Cell </li></ul>
    2. 2. <ul><li>Cell: </li></ul><ul><li>A basic unit of living matter separated from its environment by a plasma membrane. </li></ul><ul><li>The smallest structural unit of life. </li></ul>
    3. 3. <ul><li>Cell Theory: Developed in late 1800s. </li></ul><ul><li>1. All living organisms are made up of one or more cells. </li></ul><ul><li>2. The smallest living organisms are single cells, and cells are the functional units of multicellular organisms. </li></ul><ul><li>3. All cells arise from preexisting cells. </li></ul>
    4. 4. <ul><li>Microscope Features </li></ul><ul><ul><li>Magnification : </li></ul></ul><ul><ul><li>Increase in apparent size of an object. </li></ul></ul><ul><ul><li>Ratio of image size to specimen size. </li></ul></ul><ul><ul><li>Resolving power : Measures clarity of image. </li></ul></ul><ul><ul><li>Ability to see fine detail. </li></ul></ul><ul><ul><li>Ability to distinguish two objects as separate. </li></ul></ul><ul><ul><li>Minimum distance between 2 points at which they can be distinguished as separate and distinct. </li></ul></ul>
    5. 5. <ul><li>Microscopes </li></ul><ul><li>Light Microscopes: Earliest microscopes used. </li></ul><ul><li>Lenses pass visible light through a specimen. </li></ul><ul><ul><li>Magnification : Highest possible from 1000 X to 2000 X. </li></ul></ul><ul><ul><li>Resolving power : Up to 0.2  m (1  m = 1/1000 mm). </li></ul></ul>
    6. 6. <ul><li>Types of Microscope </li></ul><ul><li>Electron Microscopes: Developed in 1950s. Electron beam passes through specimen. </li></ul><ul><ul><li>Magnification : Up to 200,000 X. </li></ul></ul><ul><ul><li>Resolving power : Up to 0.2 nm (1nm = 1/1’000,000 mm). </li></ul></ul><ul><ul><li>Two types of electron microscopes: </li></ul></ul><ul><ul><li>1. Scanning Electron Microscope: Used to study cell or virus surfaces. </li></ul></ul><ul><ul><li>2. Transmission Electron Microscope: Used to study internal cell structures. </li></ul></ul>
    7. 7. <ul><li>Components of All Cells: </li></ul><ul><ul><li>1. Plasma membrane : Separates cell contents from outside environment. Made up of phospholipid bilayers and proteins. </li></ul></ul><ul><ul><li>2. Cytoplasm : Liquid, jelly-like material inside cell. </li></ul></ul><ul><ul><li>3. Ribosomes : Necessary for protein synthesis. </li></ul></ul>
    8. 8. Procaryotic versus Eucaryotic Cells Feature Procaryotic Eucaryotic Organisms Bacteria All others (animals, plants, fungi, and protozoa) Nucleus Abzsent Present DNA One chromosome Multiple chromosomes Size Small (1-10 um) Large (10 or more um) Membrane Absent Present (mitochondria, Bound golgi, chloroplasts, etc.) Organelles Division Rapid process Complex process (Binary fission) (Mitosis)
    9. 9. <ul><li>Relative Sizes of Structures </li></ul><ul><ul><ul><li>1 nanometer (10 -9 m) water molecule </li></ul></ul></ul><ul><ul><ul><li>10 nanomters (10 -8 m) small protein </li></ul></ul></ul><ul><ul><ul><li>100 nanometers (10 -7 m) HIV virus </li></ul></ul></ul><ul><ul><ul><li>1 micron (10 -6 m) cell vacuole </li></ul></ul></ul><ul><ul><ul><li>10 microns (10 -5 m) bacterium </li></ul></ul></ul><ul><ul><ul><li>100 microns (10 -4 m) large plant cell </li></ul></ul></ul><ul><ul><ul><li>1 millimeter (10 -3 m) single cell embryo </li></ul></ul></ul>
    10. 10. Relative Sizes of Procaryotic and Eucaryotic Cells and Viruses
    11. 11. Relative Sizes of Cells and Other Objects
    12. 12. <ul><li>Prokaryotic Cells </li></ul><ul><ul><ul><li>Bacteria and blue-green algae. </li></ul></ul></ul><ul><ul><ul><li>Small size : Range from 1- 10 micrometers in length. About one tenth of eukaryotic cell. </li></ul></ul></ul><ul><ul><ul><li>No nucleus : DNA in cytoplasm or nucleoid region. </li></ul></ul></ul><ul><ul><ul><li>Ribosomes are used to make proteins </li></ul></ul></ul><ul><ul><ul><li>Cell wall : Hard shell around membrane </li></ul></ul></ul><ul><ul><ul><li>Other structures that may be present: </li></ul></ul></ul><ul><ul><ul><ul><li>Capsule : Protective, outer sticky layer. May be used for attachment or to evade immune system. </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Pili : Hair-like projections (attachment) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Flagellum : Longer whip-like projection (movement) </li></ul></ul></ul></ul>
    13. 13. Procaryotic Cells: Lack a Nucleus and other Membrane Bound Organelles
    14. 14. <ul><li>Eucaryotic Cells </li></ul><ul><ul><li>Include protist, fungi, plant, and animal cells. </li></ul></ul><ul><ul><li>Nucleus : Protects and houses DNA </li></ul></ul><ul><ul><li>Membrane-bound Organelles : Internal structures with specific functions. </li></ul></ul><ul><ul><ul><li>Separate and store compounds </li></ul></ul></ul><ul><ul><ul><li>Store energy </li></ul></ul></ul><ul><ul><ul><li>Work surfaces </li></ul></ul></ul><ul><ul><ul><li>Maintain concentration gradients </li></ul></ul></ul>
    15. 15. <ul><li>Membrane-Bound Organelles of Eucaryotic Cells </li></ul><ul><ul><ul><li>Nucleus </li></ul></ul></ul><ul><ul><ul><li>Rough Endoplasmic Reticulum (RER) </li></ul></ul></ul><ul><ul><ul><li>Smooth Endoplasmic Reticulum (SER) </li></ul></ul></ul><ul><ul><ul><li>Golgi Apparatus </li></ul></ul></ul><ul><ul><ul><li>Lysosomes </li></ul></ul></ul><ul><ul><ul><li>Vacuoles </li></ul></ul></ul><ul><ul><ul><li>Chloroplasts </li></ul></ul></ul><ul><ul><ul><li>Mitochondria </li></ul></ul></ul>
    16. 16. Eucaryotic Cells: Typical Animal Cell
    17. 17. Eucaryotic Cells: Typical Plant Cell
    18. 18. <ul><li>Nucleus </li></ul><ul><ul><li>Structure </li></ul></ul><ul><ul><ul><li>Double nuclear membrane ( envelope ) </li></ul></ul></ul><ul><ul><ul><li>Large nuclear pores </li></ul></ul></ul><ul><ul><ul><li>DNA (genetic material) is combined with histones and exists in two forms: </li></ul></ul></ul><ul><ul><ul><ul><li>Chromatin ( Loose, threadlike DNA , most of cell life) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Chromosomes ( Tightly packaged DNA . Found only during cell division) </li></ul></ul></ul></ul><ul><ul><ul><li>Nucleolus : Dense region where ribosomes are made </li></ul></ul></ul><ul><ul><li>Functions </li></ul></ul><ul><ul><ul><li>House and protect cell’s genetic information (DNA) </li></ul></ul></ul><ul><ul><ul><li>Ribosome synthesis </li></ul></ul></ul>
    19. 19. Structure of Cell Nucleus
    20. 20. <ul><li>Endoplasmic Reticulum (ER) </li></ul><ul><ul><li>“ Network within the cell” </li></ul></ul><ul><ul><li>Extensive maze of membranes that branches throughout cytoplasm. </li></ul></ul><ul><ul><li>ER is continuous with plasma membrane and outer nucleus membrane. </li></ul></ul><ul><ul><li>Two types of ER: </li></ul></ul><ul><ul><ul><li>Rough Endoplasmic Reticulum (RER) </li></ul></ul></ul><ul><ul><ul><li>Smooth Endoplasmic Reticulum (SER) </li></ul></ul></ul>
    21. 21. <ul><li>Rough Endoplasmic Reticulum (RER) </li></ul><ul><ul><li>Flat, interconnected, rough membrane sacs </li></ul></ul><ul><ul><li>“ Rough” : Outer walls are covered with ribosomes. </li></ul></ul><ul><ul><li>Ribosomes : Protein making “machines”. </li></ul></ul><ul><ul><li>May exist free in cytoplasm or attached to ER. </li></ul></ul><ul><ul><li>RER Functions : </li></ul></ul><ul><ul><ul><li>Synthesis of cell and organelle membranes . </li></ul></ul></ul><ul><ul><ul><li>Synthesis and modification of proteins . </li></ul></ul></ul><ul><ul><ul><li>Packaging, and transport of proteins that are secreted from the cell. </li></ul></ul></ul><ul><ul><ul><ul><li>Example: Antibodies </li></ul></ul></ul></ul>
    22. 22. Rough Endoplasmic Reticulum (RER)
    23. 23. <ul><li>Smooth Endoplasmic Reticulum (SER) </li></ul><ul><ul><li>Network of interconnected tubular smooth membranes. </li></ul></ul><ul><ul><li>“ Smooth” : No ribosomes </li></ul></ul><ul><ul><li>SER Functions : </li></ul></ul><ul><ul><ul><li>Synthesis of phospholipids, fatty acids, and steroids (sex hormones). </li></ul></ul></ul><ul><ul><ul><li>Breakdown of toxic compounds (drugs, alcohol, amphetamines, sedatives, antibiotics, etc.). </li></ul></ul></ul><ul><ul><ul><li>Helps develop tolerance to drugs and alcohol. </li></ul></ul></ul><ul><ul><ul><li>Regulates levels of sugar released from liver into the blood </li></ul></ul></ul><ul><ul><ul><li>Calcium storage for cell and muscle contraction. </li></ul></ul></ul>
    24. 24. Smooth Endoplasmic Reticulum (SER)
    25. 25. <ul><li>Golgi Apparatus </li></ul><ul><ul><li>Stacks of flattened membrane sacs that may be distended in certain regions. Sacs are not interconnected. </li></ul></ul><ul><ul><li>First described in 1898 by Camillo Golgi (Italy). </li></ul></ul><ul><ul><li>Works closely with the ER to secrete proteins. </li></ul></ul><ul><ul><li>Golgi Functions : </li></ul></ul><ul><ul><ul><li>Receiving side receives proteins in transport vesicles from ER. </li></ul></ul></ul><ul><ul><ul><li>Modifies proteins into final shape, sorts, and labels proteins for proper transport. </li></ul></ul></ul><ul><ul><ul><li>Shipping side packages and sends proteins to cell membrane for export or to other parts of the cell. </li></ul></ul></ul><ul><ul><ul><li>Packages digestive enzymes in lysosomes . </li></ul></ul></ul>
    26. 26. The Golgi Apparatus: Receiving, Processing, and Shipping of Proteins
    27. 27. <ul><li>Lysosomes </li></ul><ul><ul><li>Small vesicles released from Golgi containing at least 40 different digestive enzymes , which can break down carbohydrates, proteins, lipids, and nucleic acids. </li></ul></ul><ul><ul><li>Optimal pH for enzymes is about 5 </li></ul></ul><ul><ul><li>Found mainly in animal cells. </li></ul></ul><ul><ul><li>Lysosome Functions : </li></ul></ul><ul><ul><ul><li>Molecular garbage dump and recycler of macromolecules (e.g.: proteins). </li></ul></ul></ul><ul><ul><ul><li>Destruction of foreign material, bacteria, viruses, and old or damaged cell components. </li></ul></ul></ul><ul><ul><ul><li>Digestion of food particles taken in by cell. </li></ul></ul></ul><ul><ul><ul><li>After cell dies, lysosomal membrane breaks down, causing rapid self-destruction . </li></ul></ul></ul>
    28. 28. Lysosomes: Intracellular Digestion
    29. 29. <ul><li> Lysosomes, Aging, and Disease </li></ul><ul><ul><li>As we get older, our lysosomes become leaky, releasing enzymes which cause tissue damage and inflammation. </li></ul></ul><ul><ul><ul><li>Example: Cartilage damage in arthritis. </li></ul></ul></ul><ul><ul><li>Steroids or cortisone-like anti-inflammatory agents stabilize lysosomal membranes, but have other undesirable effects (affect immune function). </li></ul></ul><ul><ul><li>Diseases from “ mutant ” lysosome enzymes are usually fatal: </li></ul></ul><ul><ul><ul><li>Pompe’s disease : Defective glycogen breakdown in liver. </li></ul></ul></ul><ul><ul><ul><li>Tay-Sachs disease : Defective lipid breakdown in brain. Common genetic disorder among Jewish people. </li></ul></ul></ul>
    30. 30. <ul><li>Vacuoles </li></ul><ul><ul><li>Membrane bound sac. </li></ul></ul><ul><ul><li>Different sizes, shapes, and functions: </li></ul></ul><ul><ul><ul><li>Central vacuole : In plant cells. Store starch, water, pigments, poisons, and wastes. May occupy up to 90% of cell volume. </li></ul></ul></ul><ul><ul><ul><li>Contractile vacuole : Regulate water balance, by removing excess water from cell. Found in many aquatic protists. </li></ul></ul></ul><ul><ul><ul><li>Food or Digestion Vacuole : Engulf nutrients in many protozoa (protists). Fuse with lysosomes to digest food particles. </li></ul></ul></ul>
    31. 31. Central Vacuole in a Plant Cell
    32. 32. Interactions Between Membrane Bound Organelles of Eucaryotic Cells
    33. 33. <ul><li>Chloroplasts </li></ul><ul><ul><li>Site of photosynthesis in plants and algae. </li></ul></ul><ul><ul><li>CO 2 + H 2 O + Sun Light -----> Sugar + O 2 </li></ul></ul><ul><ul><li>Number may range from 1 to over 100 per cell. </li></ul></ul><ul><ul><li>Disc shaped structure with three different membrane systems: </li></ul></ul><ul><ul><ul><li>1. Outer membrane : Covers chloroplast surface. </li></ul></ul></ul><ul><ul><ul><li>2. Inner membrane : Contains enzymes needed to make glucose during photosynthesis. Encloses stroma (liquid) and thylakoid membranes. </li></ul></ul></ul><ul><ul><ul><li>3. Thylakoid membranes: Contain chlorophyll, green pigment that traps solar energy. Organized in stacks called grana . </li></ul></ul></ul>
    34. 34. Chloroplasts Trap Solar Energy and Convert it to Chemical Energy
    35. 35. <ul><li>Chloroplasts </li></ul><ul><ul><li>Contain their own DNA, ribosomes, and make some proteins. </li></ul></ul><ul><ul><li>Can divide to form daughter chloroplasts. </li></ul></ul><ul><ul><li>Type of plastid : Organelle that produces and stores food in plant and algae cells. </li></ul></ul><ul><ul><li>Other plastids include: </li></ul></ul><ul><ul><ul><li>Leukoplasts : Store starch. </li></ul></ul></ul><ul><ul><ul><li>Chromoplasts : Store other pigments that give plants and flowers color. </li></ul></ul></ul>
    36. 36. <ul><li>Mitochondria (Sing. Mitochondrion) </li></ul><ul><ul><li>Site of cellular respiration: </li></ul></ul><ul><ul><li>Food (sugar) + O 2 -----> CO 2 + H 2 O + ATP </li></ul></ul><ul><ul><li>Change chemical energy of molecules into the useable energy of the ATP molecule. </li></ul></ul><ul><ul><li>Oval or sausage shaped. </li></ul></ul><ul><ul><li>Contain their own DNA, ribosomes, and make some proteins. </li></ul></ul><ul><ul><li>Can divide to form daughter mitochondria. </li></ul></ul><ul><ul><li>Structure: </li></ul></ul><ul><ul><ul><li>Inner and outer membranes. </li></ul></ul></ul><ul><ul><ul><li>Intermembrane space </li></ul></ul></ul><ul><ul><ul><li>Cristae (inner membrane extensions) </li></ul></ul></ul><ul><ul><ul><li>Matrix (inner liquid) </li></ul></ul></ul>
    37. 37. Mitochondria Harvest Chemical Energy From Food
    38. 38. Origin of Eucaryotic Cells <ul><ul><li>Endosymbiont Theory : Belief that chloroplasts and mitochondria were at one point independent cells that entered and remained inside a larger cell. </li></ul></ul><ul><ul><ul><li>Both organelles contain their own DNA </li></ul></ul></ul><ul><ul><ul><li>Have their own ribosomes and make their own proteins. </li></ul></ul></ul><ul><ul><ul><li>Replicate independently from cell, by binary fission. </li></ul></ul></ul><ul><ul><li>Symbiotic relationship </li></ul></ul><ul><ul><ul><li>Larger cell obtains energy or nutrients </li></ul></ul></ul><ul><ul><ul><li>Smaller cell is protected by larger cell. </li></ul></ul></ul>
    39. 39. <ul><li>The Cytoskeleton </li></ul><ul><li>Complex network of thread-like and tube-like structures. </li></ul><ul><li>Functions: Movement, structure, and structural support. </li></ul><ul><li>Three Cytoskeleton Components: </li></ul><ul><ul><li>1. Microfilaments : Smallest cytoskeleton fibers. Important for: </li></ul></ul><ul><ul><ul><li>Muscle contraction : Actin & myosin fibers in muscle cells </li></ul></ul></ul><ul><ul><ul><li>“ Amoeboid motion ” of white blood cells </li></ul></ul></ul>
    40. 40. Components of the Cytoskeleton are Important for Structure and Movement
    41. 41. <ul><li>Three Cytoskeleton Components: </li></ul><ul><ul><li>2. Intermediate filaments : Medium sized fibers </li></ul></ul><ul><ul><ul><li>Anchor organelles (nucleus) and hold cytoskeleton in place. </li></ul></ul></ul><ul><ul><ul><li>Abundant in cells with high mechanical stress. </li></ul></ul></ul><ul><ul><li>3. Microtubules : Largest cytoskeleton fibers. Found in: </li></ul></ul><ul><ul><ul><li>Centrioles : A pair of structures that help move chromosomes during cell division (mitosis and meiosis). </li></ul></ul></ul><ul><ul><ul><li>Found in animal cells, but not plant cells. </li></ul></ul></ul><ul><ul><ul><li>Movement of flagella and cilia . </li></ul></ul></ul>
    42. 42. <ul><li>Typical Animal Cell </li></ul>
    43. 43. Cilia and Flagella <ul><ul><li>Projections used for locomotion or to move substances along cell surface. </li></ul></ul><ul><ul><li>Enclosed by plasma membrane and contain cytoplasm. </li></ul></ul><ul><ul><li>Consist of 9 pairs of microtubules surrounding two single microtubules (9 + 2 arrangement). </li></ul></ul><ul><li>Flagella: Large whip-like projections. </li></ul><ul><ul><li>Move in wavelike manner, used for locomotion. </li></ul></ul><ul><ul><ul><li>Example: Sperm cell </li></ul></ul></ul><ul><li>Cilia: Short hair-like projections. </li></ul><ul><ul><ul><li>Example: Human respiratory system uses cilia to remove harmful objects from bronchial tubes and trachea. </li></ul></ul></ul>
    44. 44. Structure of Eucaryotic Flagellum
    45. 45. Cell Surfaces <ul><li>A. Cell wall: Much thicker than cell membrane, </li></ul><ul><li>(10 to 100 X thicker). </li></ul><ul><li>Provides support and protects cell from lysis. </li></ul><ul><ul><li>Plant and algae cell wall: Cellulose </li></ul></ul><ul><ul><li>Fungi and bacteria have other polysaccharides. </li></ul></ul><ul><ul><li>Not present in animal cells or protozoa . </li></ul></ul><ul><li>Plasmodesmata: Channels between adjacent plant cells form a circulatory and communication system between cells. </li></ul><ul><ul><li>Sharing of nutrients, water, and chemical messages. </li></ul></ul>
    46. 46. Plasmodesmata: Communication Between Adjacent Plant Cells
    47. 47. Cell Surfaces <ul><li>B. Extracellular matrix: Sticky layer of glycoproteins found in animal cells. </li></ul><ul><li>Important for attachment, support, protection, and response to environmental stimuli. </li></ul><ul><li>Junctions Between Animal Cells: </li></ul><ul><ul><li>Tight Junctions : Bind cells tightly, forming a leakproof sheet. Example: Between epithelial cells in stomach lining. </li></ul></ul><ul><ul><li>Anchoring Junctions : Rivet cells together, but still allow material to pass through spaces between cells. </li></ul></ul><ul><ul><li>Communicating Junctions : Similar to plasmodesmata in plants. Allow water and other small molecules to flow between neighboring cells. </li></ul></ul>
    48. 48. Different Animal Cell Junctions
    49. 49. Important Differences Between Plant and Animal Cells <ul><ul><li>Plant cells Animal cells </li></ul></ul><ul><ul><li>Cell wall None (Extracellular matrix) </li></ul></ul><ul><ul><li>Chloroplasts No chloroplasts </li></ul></ul><ul><ul><li>Large central vacuole No central vacuole </li></ul></ul><ul><ul><li>Flagella rare Flagella more usual </li></ul></ul><ul><ul><li>No Lysosomes Lysosomes present </li></ul></ul><ul><ul><li>No Centrioles Centrioles present </li></ul></ul>
    50. 50. Differences Between Plant and Animal Cells Animal Cell Plant Cell
    51. 51. <ul><li>Typical Plant Cell </li></ul>
    52. 52. Summary of Eucaryotic Organelles <ul><li>Function: Manufacture </li></ul><ul><ul><li>Nucleus </li></ul></ul><ul><ul><li>Ribosomes </li></ul></ul><ul><ul><li>Rough ER </li></ul></ul><ul><ul><li>Smooth ER </li></ul></ul><ul><ul><li>Golgi Apparatus </li></ul></ul><ul><li>Function: Breakdown </li></ul><ul><ul><li>Lysosomes </li></ul></ul><ul><ul><li>Vacuoles </li></ul></ul>
    53. 53. Summary of Eucaryotic Organelles <ul><li>Function: Energy Processing </li></ul><ul><ul><li>Chloroplasts (Plants and algae) </li></ul></ul><ul><ul><li>Mitochondria </li></ul></ul><ul><li>Function: Support, Movement, Communication </li></ul><ul><ul><li>Cytoskeleton (Cilia, flagella, and centrioles) </li></ul></ul><ul><ul><li>Cell walls (Plants, fungi, bacteria, and some protists) </li></ul></ul><ul><ul><li>Extracellular matrix (Animals) </li></ul></ul><ul><ul><li>Cell junctions </li></ul></ul>
    54. 54. <ul><li>The Cell Membrane and Cell Transport </li></ul>
    55. 55. <ul><li>Functions of Cell Membranes </li></ul><ul><li>1. Separate cell from nonliving environment. Form most organelles and partition cell into discrete compartments. </li></ul><ul><li>2. Regulate passage of materials in and out of the cell and organelles. Membrane is selectively permeable. </li></ul><ul><li>3. Receive information that permits cell to sense and respond to environmental changes. </li></ul><ul><ul><ul><li>Hormones </li></ul></ul></ul><ul><ul><ul><li>Growth factors </li></ul></ul></ul><ul><ul><ul><li>Neurotransmitters </li></ul></ul></ul><ul><li>4. Communication with other cells and the organism as a whole. Surface proteins allow cells to recognize each other, adhere, and exchange materials. </li></ul>
    56. 56. <ul><li>I. Fluid Mosaic Model of the Membrane </li></ul><ul><ul><li>1. Phospholipid bilayer : Major component is a phospholipid bilayer. </li></ul></ul><ul><ul><ul><li>Hydrophobic tails face inward </li></ul></ul></ul><ul><ul><ul><li>Hydrophilic heads face water </li></ul></ul></ul><ul><ul><li>2. Mosaic of proteins : Proteins “float” in the phospholipid bilayer. </li></ul></ul><ul><ul><li>3. Cholesterol: Maintains proper membrane fluidity. </li></ul></ul><ul><ul><li>The outer and inner membrane surfaces are different . </li></ul></ul>
    57. 57. Membrane Phospholipids Form a Bilayer
    58. 58. The Membrane is a Fluid Mosaic of Phospholipids and Proteins Notice that inner and outer surfaces are different
    59. 59. <ul><ul><li>A. Fluid Quality of Plasma Membranes </li></ul></ul><ul><ul><li>In a living cell, membrane has same fluidity as salad oil. </li></ul></ul><ul><ul><ul><li>Unsaturated hydrocarbon tails INCREASE membrane fluidity </li></ul></ul></ul><ul><ul><li>Phospholipids and proteins drift laterally. </li></ul></ul><ul><ul><ul><li>Phospholipids move very rapidly </li></ul></ul></ul><ul><ul><ul><li>Proteins drift in membrane more slowly </li></ul></ul></ul><ul><ul><li>Cholesterol : Alters fluidity of the membrane </li></ul></ul><ul><ul><ul><li>Decreases fluidity at warmer temperatures (> 37 o C) </li></ul></ul></ul><ul><ul><ul><li>Increases fluidity at lower temperatures (< 37 o C) </li></ul></ul></ul>
    60. 60. <ul><ul><li>B. Membranes Contain Two Types of Proteins </li></ul></ul><ul><ul><li>1. Integral membrane proteins : </li></ul></ul><ul><ul><li>Inserted into the membrane. </li></ul></ul><ul><ul><li>Hydrophobic region is adjacent to hydrocarbon tails. </li></ul></ul><ul><ul><li>2. Peripheral membrane proteins : </li></ul></ul><ul><ul><li>Attached to either the inner or outer membrane surface. </li></ul></ul><ul><ul><li>Functions of Membrane Proteins: </li></ul></ul><ul><ul><li>1. Transport of materials across membrane </li></ul></ul><ul><ul><li>2. Enzymes </li></ul></ul><ul><ul><li>3. Receptors of chemical messengers </li></ul></ul><ul><ul><li>4. Identification: Cell-cell recognition </li></ul></ul><ul><ul><li>5. Attachment: </li></ul></ul><ul><ul><ul><li>Membrane to cytoskeleton </li></ul></ul></ul><ul><ul><ul><li>Intercellular junctions </li></ul></ul></ul>
    61. 61. Membrane Proteins Have Diverse Functions
    62. 62. <ul><ul><li>C. Membrane Carbohydrates and Cell-Cell Recognition </li></ul></ul><ul><ul><li>Found on outside surface of membrane. </li></ul></ul><ul><ul><li>Important for Cell-cell recognition : Ability of one cell to “recognize” other cells. </li></ul></ul><ul><ul><ul><li>Allows immune system to recognize self/non-self </li></ul></ul></ul><ul><ul><ul><li>Include : </li></ul></ul></ul><ul><ul><ul><ul><li>Glycolipids: Lipids with sugars </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Glycoproteins: Proteins with sugars </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Major histocompatibility proteins (MHC or transplantation antigens ). </li></ul></ul></ul></ul><ul><ul><ul><li>Vary greatly among individuals and species. </li></ul></ul></ul><ul><ul><ul><li>Organ transplants require matching of cell markers and/or immune suppression. </li></ul></ul></ul>
    63. 64. <ul><li>The cell plasma membrane is Selectively Permeable </li></ul><ul><li>A. Permeability of the Lipid Bilayer </li></ul><ul><ul><ul><li>1. Non-polar (Hydrophobic) Molecules </li></ul></ul></ul><ul><ul><ul><ul><li>Dissolve into the membrane and cross with ease </li></ul></ul></ul></ul><ul><ul><ul><ul><li>The smaller the molecule, the easier it can cross </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Examples: O 2 , hydrocarbons, steroids </li></ul></ul></ul></ul><ul><ul><ul><li>2. Polar (Hydrophilic) Molecules </li></ul></ul></ul><ul><ul><ul><ul><li>Small polar uncharged molecules can pass through easily (e.g.: H 2 O , CO 2 ) </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Large polar uncharged molecules pass with difficulty (e.g.: glucose) </li></ul></ul></ul></ul><ul><ul><ul><li>3. Ionic (Hydrophilic) Molecules </li></ul></ul></ul><ul><ul><ul><ul><li>Charged ions or particles cannot get through </li></ul></ul></ul></ul><ul><ul><ul><ul><li>(e.g.: ions such as Na + , K + , Cl - ) </li></ul></ul></ul></ul>
    64. 65. <ul><ul><li>Transport Proteins in the membrane : Integral membrane proteins that allow for the transport of specific molecules across the phospholipid bilayer of the plasma membrane. </li></ul></ul><ul><ul><li>How do they work? </li></ul></ul><ul><ul><ul><li>May provide a “hydrophilic tunnel” (channel) </li></ul></ul></ul><ul><ul><ul><li>May bind to molecule and physically move it </li></ul></ul></ul><ul><ul><ul><li>Are specific for the atom/molecule transported </li></ul></ul></ul>
    65. 66. <ul><li>III. Passive transport: Diffusion of molecules across the plasma membrane </li></ul><ul><ul><li>A. Diffusion : The net movement of a substance from an area of high concentration to area of low concentration. </li></ul></ul><ul><ul><li>Does not require energy. </li></ul></ul><ul><ul><li>B. Passive transport : The diffusion of substance across a biological membrane. </li></ul></ul><ul><ul><ul><li>Only substances which can cross bilayer by themselves or with the aid of a protein </li></ul></ul></ul><ul><ul><ul><li>Does not require the cell’s energy </li></ul></ul></ul>
    66. 67. Passive Transport: Diffusion Across a Membrane Does Not Require Energy
    67. 68. <ul><li>IV. Osmosis : </li></ul><ul><li>The diffusion of water across a semi-permeable membrane. </li></ul><ul><li>Through osmosis water will move from an area with higher water concentration to an area with lower water concentration. </li></ul><ul><li>Solutes can’t move across the semi-permeable membrane. </li></ul>
    68. 70. <ul><li>Osmotic Pressure : Ability of a solution to take up water through osmosis. </li></ul><ul><ul><li>Example: The cytoplasm of a cell has a certain osmotic pressure caused by the solutes it contains. </li></ul></ul><ul><ul><li>There are three different types of solution when compared to the interior (cytoplasm) of a cell: </li></ul></ul><ul><ul><li>1. Hypertonic solution : Higher osmotic pressure than cell due to: </li></ul></ul><ul><ul><li>Higher solute concentration than cell or </li></ul></ul><ul><ul><li>Lower water concentration than cell. </li></ul></ul><ul><ul><li>2. Hypotonic solution : Lower osmotic pressure than cell due to: </li></ul></ul><ul><ul><li>Lower solute concentration than cell or </li></ul></ul><ul><ul><li>Higher water concentration than cell. </li></ul></ul><ul><ul><li>3. Isotonic solution : Same osmotic pressure than cell. </li></ul></ul><ul><ul><li>Equal concentration of solute(s) and water than cell. </li></ul></ul>
    69. 71. <ul><li>V. Cells depend on proper water balance </li></ul><ul><ul><li>Animal Cells: </li></ul></ul><ul><ul><li>Do best in isotonic solutions. </li></ul></ul><ul><ul><li>Examples: </li></ul></ul><ul><ul><ul><li>0.9% NaCl (Saline) </li></ul></ul></ul><ul><ul><ul><li>5% Glucose </li></ul></ul></ul><ul><ul><li>If solution is not isotonic, cell will be affected: </li></ul></ul><ul><ul><li>Hypertonic solution : Cell undergoes crenation. Cell “shrivels” or shrinks. </li></ul></ul><ul><ul><ul><li>Example: 5% NaCl or 10% glucose </li></ul></ul></ul><ul><ul><li>Hypotonic solution: Cell undergoes lysis. Cell swells and eventually bursts. </li></ul></ul><ul><ul><ul><li>Example: Pure water. </li></ul></ul></ul>
    70. 72. <ul><li>V. Cells depend on proper water balance </li></ul><ul><ul><li>Plant Cells : Do best in hypotonic solutions, because the cell wall protects from excessive uptake of water. </li></ul></ul><ul><ul><li>Hypertonic solution: Cell undergoes plasmolysis. Cell membrane shrivels inside cell wall. </li></ul></ul><ul><ul><li>Isotonic solution: Cell becomes flaccid or wilts. </li></ul></ul><ul><ul><li>Hypotonic solution: Turgor. Increased firmness of cells due to osmotic pressure. </li></ul></ul><ul><ul><ul><li>This is the reason why supermarkets spray fruits and vegetables with pure water, making them look firm and fresh. </li></ul></ul></ul>
    71. 74. <ul><li>VI. Facilitated Diffusion: </li></ul><ul><li>Some substances cannot cross the membrane by themselves due to their size or charge. </li></ul><ul><li>Membrane proteins facilitate the transport of solutes down their concentration gradient. </li></ul><ul><li>No cell energy is required. </li></ul><ul><ul><li>Transport Proteins </li></ul></ul><ul><ul><li>Specific : Only transport very specific molecules (binding site) </li></ul></ul><ul><ul><ul><li>Glucose </li></ul></ul></ul><ul><ul><ul><li>Specific ions (Na + , K + , Cl - ) </li></ul></ul></ul>
    72. 75. Facilitated Diffusion Uses a Membrane Transport Protein
    73. 76. <ul><li>VI. Active Transport : </li></ul><ul><li>Proteins use energy from ATP to actively “pump” solutes across the membrane </li></ul><ul><li>Solutes are moved against a concentration gradient. </li></ul><ul><li>Energy is required. </li></ul><ul><ul><li>Example : </li></ul></ul><ul><ul><li>The Na + -K + ATPase pump: </li></ul></ul><ul><ul><li>Energy of ATP hydrolysis is used to move Na + out of the cell and K + into the cell </li></ul></ul>
    74. 78. <ul><li>Endocytosis : </li></ul><ul><li>Moving materials into cell with vesicles . </li></ul><ul><li>Requires use of cell energy. </li></ul><ul><li>1. Pinocytosis (“Cell drinking”): Small droplets of liquid are taken into the cell through tiny vesicles. </li></ul><ul><li>Not a specific process, all solutes in droplets are taken in. </li></ul><ul><li>2. Phagocytosis (“Cell eating”): Large solid particles are taken in by cell. </li></ul><ul><li>Example: Amoebas take in food particles by surrounding them with cytoplasmic extensions called pseudopods. </li></ul><ul><li>Particles are surrounded by a vacuole. </li></ul><ul><li>Vacuole later fuses with the lysosome and contents are digested. </li></ul>
    75. 79. Endocytosis Uses Vesicles to Move Substances into the Cell
    76. 80. <ul><li>Endocytosis : </li></ul><ul><li>3. Receptor mediated endocytosis : Highly specific. Materials moved into cell must bind to specific receptors first. </li></ul><ul><li>Example: Low density lipoproteins (LDL) : </li></ul><ul><ul><li>Main form of cholesterol in blood. </li></ul></ul><ul><ul><li>Globule of cholesterol surrounded by single layer of phospholipids with embedded proteins. </li></ul></ul><ul><ul><li>Liver cell receptors bind to LDL proteins and remove LDLs from blood through receptor mediated endocytosis. </li></ul></ul><ul><ul><li>Familial hypercholesterolemia : Genetic disorder in which gene for the LDL receptor is mutated. Disorder found in 1 in 500 human babies worldwide. Results in unusually high levels of blood cholesterol. </li></ul></ul>
    77. 81. Blood Cholesterol is Taken Up by Liver Cells through Receptor Mediated Endocytosis
    78. 82. <ul><li>Exocytosis : </li></ul><ul><li>Used to export materials out of cell. </li></ul><ul><li>Materials in vesicles fuse with cell membrane and are released to outside. </li></ul><ul><ul><ul><li>Tear glands export salty solution. </li></ul></ul></ul><ul><ul><ul><li>Pancreas uses exocytosis to secrete insulin. </li></ul></ul></ul>