Collagen Structure and Function
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Questions and Answers

What is the primary function of tight junctions in epithelial cells?

  • To serve as barriers to solute diffusion (correct)
  • To facilitate cell migration
  • To enable solute diffusion
  • To regulate cell proliferation

    • What is the role of ZO proteins in tight junctions?

  • To regulate cell migration
  • To bind to claudins and occludins
  • To facilitate cell-cell adhesion
  • To act as a scaffold (correct)

    • What is the primary function of cadherins in epithelial cells?

  • To facilitate solute diffusion
  • To regulate cell migration
  • To mediate heterophilic interactions with the ECM
  • To mediate homophilic cell-cell adhesion (correct)

    • What is the role of integrins in epithelial cells?

    <p>To mediate heterophilic interactions with the ECM</p> Signup and view all the answers

    What is the primary component of the ECM that provides structural support?

    <p>Collagen fibers</p> Signup and view all the answers

    What is the process by which lymphocytes migrate into tissues?

    <p>Mediated by integrins</p> Signup and view all the answers

    What is the primary component of ECM produced by fibroblasts?

    <p>Collagen fibres</p> Signup and view all the answers

    What percentage of skin is composed of collagen?

    <p>74%</p> Signup and view all the answers

    How many types of collagen proteins exist?

    <p>42</p> Signup and view all the answers

    What is the sequence found in all collagens?

    <p>Gly-Xaa-Yaa</p> Signup and view all the answers

    What is the typical structure of an α chain?

    <p>A helix with 3 aa per turn</p> Signup and view all the answers

    What is the function of proline in collagen?

    <p>Stabilizes the triple helix structure</p> Signup and view all the answers

    How are collagen polypeptide α chains arranged in a triple helix?

    <p>Wound round each other</p> Signup and view all the answers

    Where is post-translational modification of collagen chains carried out?

    <p>In the ER and extracellularly</p> Signup and view all the answers

    What is unique about the structure of matrix proteoglycans and glycosaminoglycans?

    <p>They are highly dynamic structures that are continually being produced and remodeled.</p> Signup and view all the answers

    Which cells are responsible for secreting matrix macromolecules in connective tissues?

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

    What is the primary function of the ECM in connective tissues?

    <p>To bear mechanical stresses of tension and compression.</p> Signup and view all the answers

    What is the composition of the basal lamina different from?

    <p>Connective tissue</p> Signup and view all the answers

    What is the primary function of the basal lamina?

    <p>To underlie epithelial cell sheets and surround individual muscle cells.</p> Signup and view all the answers

    What is the focus of the video series covered in Module 8?

    <p>Sorting, matrix, and migration</p> Signup and view all the answers

    What is the primary function of the TGN in polarised epithelial cells?

    <p>To sort and transport plasma membrane proteins</p> Signup and view all the answers

    What is the mechanism of protein transport in the indirect pathway?

    <p>Endocytosis and selective transport from basolateral to apical surface</p> Signup and view all the answers

    What is the role of lipid rafts in protein transport?

    <p>To sort and transport GPI-anchored proteins</p> Signup and view all the answers

    What is the function of the cytoplasmic tail of a protein?

    <p>To provide sorting signals for protein transport</p> Signup and view all the answers

    What is the direction of protein transport in the direct pathway?

    <p>From TGN to apical surface</p> Signup and view all the answers

    What is the role of the antibody to the cytoplasmic tail of the blue cargo protein?

    <p>To isolate transport vesicles</p> Signup and view all the answers

    Where do all newly synthesized proteins go first in polarised epithelial cells?

    <p>The basolateral surface</p> Signup and view all the answers

    Where does endocytosis occur in polarised epithelial cells?

    <p>From both the apical and basolateral surfaces</p> Signup and view all the answers

    Which type of protein facilitates direct contacts between the ECM and cells via cell surface receptors?

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

    What is the primary function of integrins in relation to the ECM?

    <p>To facilitate interactions between cells and the ECM</p> Signup and view all the answers

    What is the role of multiple binding domains in adhesive glycoproteins?

    <p>To increase the local protein concentration at the cell surface</p> Signup and view all the answers

    Which of the following is a characteristic of adhesive glycoproteins in the ECM?

    <p>They contain multiple binding domains</p> Signup and view all the answers

    What is the role of actin cytoskeleton in the formation of integrin-ECM interactions?

    <p>To generate the tension needed for binding and oligomerization</p> Signup and view all the answers

    Which of the following ECM components is involved in the formation of direct contacts between the ECM and cells?

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

    What is the role of integrins in the migration of lymphocytes into tissues?

    <p>To facilitate interactions between lymphocytes and the ECM</p> Signup and view all the answers

    What is the function of fibronectin and laminin in the ECM?

    <p>To form direct contacts between the ECM and cells</p> Signup and view all the answers

    Study Notes

    Experimental Rationales for Sorting Mechanisms in Epithelial Cells

    • Experimental approaches to distinguish different sorting mechanisms in epithelial cells involve understanding how membrane proteins reach the correct surface of polarized epithelial cells.
    • Two pathways exist: direct sorting of membrane proteins in the TGN (Trans-Golgi Network) and indirect sorting via endocytosis and selective transport to the apical surface.

    Integrating Cells into Organized Tissues

    • The extracellular matrix (ECM) plays a crucial role in integrating cells into organized tissues.
    • The ECM is made and oriented by the cells within it, bearing mechanical stresses of tension and compression.

    Extracellular Matrix (ECM)

    • The ECM is a highly dynamic structure continually produced and remodeled.
    • The ECM composition of basal laminae is different from connective tissue.
    • The ECM is made up of various components, including collagen, proteoglycans, and glycosaminoglycans.

    Collagen and Collagen Fibres

    • Collagen is a major fibrillar component of the ECM, found in various tissues such as cartilage, cornea, bone, and skin.
    • There are 42 types of collagen, all containing the Gly-Xaa-Yaa-sequon in tandem (10-90% of sequence).
    • Collagen has a triple helix structure, with three collagen polypeptide α chains wound around each other.
    • Proline stabilizes the helical conformation, while glycine fits into the crowded interior, allowing tight packing of the triple helix.

    Adhesive Glycoproteins of the ECM

    • Adhesive ECM glycoproteins, such as fibronectin and laminin, form direct contacts between the ECM and cells via cell surface receptors (integrins).
    • These glycoproteins contain multiple binding domains and interact with cell surface receptors, localizing fibronectin/laminin at appropriate sites for assembly and increasing local protein concentration at the cell surface.

    Cell-Cell Adhesion and Integrins

    • Cadherins mediate homophilic cell-cell adhesion, with a specific structure and molecular interactions.
    • Integrins mediate heterophilic interactions between cells and the ECM, with a specific structure, molecular interactions, and regulation.
    • Integrins play a crucial role in lymphocyte migration into tissues.

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    Description

    This quiz covers the structure and function of collagens, the major fibrillar components of the extracellular matrix (ECM). It includes the production of collagens by fibroblasts and the secretion of these large molecules.

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