Cell Biology: Extracellular Interactions
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Questions and Answers

What is the primary role of epithelium in the body?

  • Nutrient absorption
  • Cell movement
  • Fluid secretion
  • Covering surfaces and lining cavities (correct)

    • What is one function of endothelium within blood vessels?

  • Regulation of blood pressure (correct)
  • Production of hormones
  • Protection against pathogens
  • Energy storage

    • Which layer of the skin is composed of dense, irregular connective tissue?

  • Subcutaneous layer
  • Epidermis
  • Basement membrane
  • Dermis (correct)

    • Which process is NOT primarily regulated by interactions between cells and their environment?

    <p>Cell death</p> Signup and view all the answers

    What critical function does skin serve beyond being a covering?

    <p>Sensory perception</p> Signup and view all the answers

    How do cells primarily maintain their defined relationships in tissues?

    <p>By interacting with extracellular materials</p> Signup and view all the answers

    Capillaries are lined with what type of cells?

    <p>Epithelial cells</p> Signup and view all the answers

    What element is critical for the 3-D organization of tissues and organs during embryo development?

    <p>Cell migration</p> Signup and view all the answers

    What is the primary role of the glomerular basement membrane (GBM) in the kidneys?

    <p>Filters blood while retaining cells and large proteins.</p> Signup and view all the answers

    Which condition is characterized by a thickened glomerular basement membrane (GBM)?

    <p>Diabetes</p> Signup and view all the answers

    What type of collagen is most abundant in the human body?

    <p>Collagen type I</p> Signup and view all the answers

    What is a possible effect of Vitamin C deficiency related to collagen?

    <p>Scurvy leading to poor wound healing.</p> Signup and view all the answers

    Which type of collagen is primarily found in the cartilage?

    <p>Collagen type II</p> Signup and view all the answers

    What genetic condition is associated with collagen type I abnormalities?

    <p>Osteogenesis Imperfecta</p> Signup and view all the answers

    What role does hydroxylated proline play in collagen structure?

    <p>Stabilizes the triple helix of collagen.</p> Signup and view all the answers

    Which type of collagen provides mechanical support with flexibility and is found in basement membranes?

    <p>Collagen type IV</p> Signup and view all the answers

    Which condition presents with distinct facial appearance, bruising, and skin thinning due to type III collagen issues?

    <p>Ehlers-Danlos Syndrome (type 4)</p> Signup and view all the answers

    What is the main source of collagen production in the body?

    <p>Fibroblasts</p> Signup and view all the answers

    What is the primary function of tight junctions in cell-cell interactions?

    <p>Seal gaps between cells</p> Signup and view all the answers

    Which type of junction connects actin filaments between cells?

    <p>Adherens junctions</p> Signup and view all the answers

    What role does the glycocalyx play in cellular interactions?

    <p>Mediates cell-cell and cell-substratum interactions</p> Signup and view all the answers

    Which structure anchors intermediate filaments to the extracellular matrix?

    <p>Hemidesmosomes</p> Signup and view all the answers

    What is the primary component of the extracellular matrix that strengthens tissue?

    <p>Basement membrane</p> Signup and view all the answers

    What is one of the main functions of the endothelial cells?

    <p>Providing a protective lining for blood vessels</p> Signup and view all the answers

    Which disease is characterized by damage to the glycocalyx?

    <p>Atherosclerosis</p> Signup and view all the answers

    What is a primary role of the extracellular matrix (ECM)?

    <p>Providing physical and biochemical signals</p> Signup and view all the answers

    Which of the following best describes the basement membrane?

    <p>Part of the extracellular matrix that underlies epithelial tissue</p> Signup and view all the answers

    In which of the following ways does the basement membrane assist epithelial cells?

    <p>Anchoring epithelial cells to connective tissue</p> Signup and view all the answers

    What is the significance of the dynamic nature of the extracellular matrix?

    <p>It's continually degraded and reformed, affecting cellular activity.</p> Signup and view all the answers

    Which of the following is NOT a function of the basement membrane?

    <p>Storing metabolic waste products</p> Signup and view all the answers

    How does the extracellular matrix contribute to tissue repair?

    <p>It provides cues for epithelial cell differentiation.</p> Signup and view all the answers

    What is the primary function of fibronectin in the extracellular matrix?

    <p>Cell adhesion and migration</p> Signup and view all the answers

    Which sequence allows fibronectin to bind to integrins?

    <p>Arg-Gly-Asp</p> Signup and view all the answers

    What structural feature do laminins share?

    <p>Three polypeptide chains linked by disulfide bonds</p> Signup and view all the answers

    Which cells primarily secrete fibronectin?

    <p>Fibroblasts</p> Signup and view all the answers

    What is a primary role of laminin in embryonic development?

    <p>Guiding cell migration of primordial germ cells</p> Signup and view all the answers

    Which components does fibronectin NOT bind to?

    <p>Lipids</p> Signup and view all the answers

    How are fibronectin monomers structured?

    <p>Two nearly identical monomers linked by disulfide bonds</p> Signup and view all the answers

    Which of the following is a function of laminin?

    <p>Cell growth and differentiation</p> Signup and view all the answers

    Study Notes

    Extracellular Interactions

    • Cells in multicellular organisms are organized into tissues
    • Cells interact with each other and extracellular materials
    • These interactions regulate cell migration, growth, differentiation, and 3D tissue organization

    Tissues

    • Epithelium: A thin layer of tightly packed cells that cover surfaces and line cavities
      • Examples: epidermis (outer layer of skin)
    • Endothelium: Specialized epithelium found inside blood vessels and lymphatic vessels
      • Single cell layer, controls bloodflow, regulates blood pressure, facilitates nutrient and waste exchange

    Cell-Cell/Cell-ECM Interactions

    • Apical Surface:
      • Tight Junctions: Seal gap between cells
      • Adherens junctions: Connect actin filaments between cells
      • Desmosome: Connects intermediate filaments between cells
      • Gap Junction: Passage of small water-soluble molecules
      • Hemidesmosome: Anchors intermediate filaments to extracellular matrix
    • Basal Surface:
      • Focal adhesions: Anchors many cell types to ECM

    Extracellular Components

    • Glycocalyx: Cell coat of glycoproteins and glycolipids that project outward from the plasma membrane
      • Located at epithelial and endothelial cells
      • Mediates cell-cell and cell-substratum interactions
      • Provides mechanical protection
    • Extracellular Matrix (ECM): Organized network of extracellular material
      • Provides physical and biochemical signals
      • Basement Membrane is part of the ECM, located beneath epithelial tissue and surrounds blood vessels, nerve fibers, muscles, and fat cells
      • Separates adjacent tissues, provides mechanical support, generates signals for cell survival, serves as substratum for cell migration, and acts as a barrier to macromolecules

    Basement Membrane in Disease

    • Glomerular basement membrane (GBM) filters blood in the kidney
      • Abnormal GBM impairs kidney filtration
      • Examples:
        • Diabetes: GBM thickens
        • Basement membrane disease: GBM becomes thin
        • GoodPasture’s syndrome: GBM is disrupted and thin

    Basement Membrane Roles

    • For Epithelium:
      • Anchorage: Anchors epithelial cells to connective tissue
      • Filtration: Controls substance exchange between epithelium and adjacent tissues
      • Compartmentalization: Separates epithelium from connective tissue
      • Cell differentiation and regeneration: Guides epithelial cell differentiation and repair
    • For Endothelium:
      • Structural support: Provides a foundation for endothelial cells
      • Selective barrier: Regulates molecule passage between blood and tissues
      • Cell migration and repair: Aids endothelial cell migration and proliferation during angiogenesis and wound healing
      • Maintains separation: Prevents mixing of endothelial cells with underlying tissues

    Extracellular Matrix Proteins

    • Collagen: Main structural protein in ECM, most abundant protein in the human body, has high tensile strength
      • Types:
        • Fibrillar: Assemble into rigid, cable-like fibrils that package into thicker fibers. Found in skin, tendons, vasculature, cornea, bone, and organs
        • Non-Fibrillar: Non-helical lattice arrangement with globular domains found in basement membranes.
    • Fibronectin: Glycoprotein secreted by fibroblasts, initially soluble, cells use it to build insoluble matrix
      • Plays a major role in cell adhesion, growth, migration, differentiation, wound healing, and embryonic development
    • Laminin: Family of extracellular glycoproteins, organized into a cross-shaped molecule
      • Binds to cell-surface receptors, other laminin molecules, proteoglycans, and collagen of the basement membrane
      • Important for cell migration, growth, and differentiation

    Collagen - Structure

    • α chains of collagen: Contain hydroxylated proline residues
      • Contribute to stability of the triple helix structure
      • Vitamin C adds hydroxyl groups to lysine and proline, crucial for collagen structure
    • Vitamin C deficiency: Leads to scurvy (poor wound healing, hair changes, skin bleeding)

    Collagen - Types and Genetic Mutations

    • Type I: Most abundant, found in tendons, skin, vessel walls, fibrocartilage, bones, and teeth
      • Mutations: Osteogenesis Imperfecta (brittle bone disease)
    • Type II: Makes up 50% of cartilage protein
      • Mutations: Dwarfism
    • Type III: Found in wound healing, vessel walls, skin, intestines, and the uterus
      • Mutations: Ehlers-Danlos Syndrome (type 4)

    Fibronectin - Structure

    • Binds to integrins (membrane-spanning receptor proteins) via Arg-Gly-Asp sequence
    • Also binds to ECM via collagen, fibrin, and proteoglycans
    • Protein dimer: Composed of 2 nearly identical monomers linked by disulfide bonds, containing distinct modules

    Laminin - Functions

    • Plays a pivotal role in the migration of primordial germ cells (PGCs)
      • PGCs arise in the yolk sac and travel to the developing gonad via regions rich in laminin.

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    Description

    Explore the fundamental interactions between cells and their surrounding extracellular matrix in multicellular organisms. This quiz covers the organization of tissues, various types of epithelium, and the specific cell-cell and cell-ECM junctions that facilitate critical biological processes. Test your knowledge on how these interactions impact cell behavior and tissue formation.

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