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Chapters 6 and 7

Chapters 6 and 7

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