Extracellular Matrix and Collagens
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Questions and Answers

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

  • It supports cell division.
  • It regulates gene expression.
  • It generates cellular energy.
  • It maintains the positional homeostasis of organs. (correct)
  • Which component is NOT considered a major molecule of the extracellular matrix?

  • Elastin
  • Proteoglycans
  • Hemoglobin (correct)
  • Collagens
  • How does the structure of the ECM change during development?

  • It becomes more rigid and less diverse.
  • It remains static and unchanging.
  • It avoids any interaction with cells.
  • It evolves in response to growth and injury. (correct)
  • Which of the following is a role of glycosaminoglycans (GAGs) in the ECM?

    <p>Providing structural integrity and hydration.</p> Signup and view all the answers

    What factor primarily determines the variation in the composition of the ECM in different organs?

    <p>The structure and chemical makeup of the ECM.</p> Signup and view all the answers

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

    <p>It consists of insoluble macromolecular networks.</p> Signup and view all the answers

    Which component contributes significantly to the hydration of the extracellular matrix?

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

    How does the extracellular matrix change during injury?

    <p>It typically undergoes restructuring and modification.</p> Signup and view all the answers

    What primarily determines the steady-state levels of ECM components?

    <p>Mechanical loading and biochemical signals.</p> Signup and view all the answers

    What type of structure does collagen primarily exhibit?

    <p>A triple-chain helix.</p> Signup and view all the answers

    Which of the following molecules is a major component of the extracellular matrix?

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

    What is the approximate size of tropocollagen?

    <p>300 nm</p> Signup and view all the answers

    Which of the following functions is NOT associated with the extracellular matrix?

    <p>Providing a site for cellular energy production.</p> Signup and view all the answers

    What is the primary structure of collagen primarily characterized by?

    <p>A Gly-X-Y amino acid repeat sequence</p> Signup and view all the answers

    Which of the following is NOT a role of glycosaminoglycans (GAGs)?

    <p>Providing tensile strength</p> Signup and view all the answers

    What characteristic of collagen allows it to form a stable triple helix structure?

    <p>Glycine residues fitting into tight junctions</p> Signup and view all the answers

    Which component is a major part of the basement membrane in the extracellular matrix?

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

    What is the predominant function of proteoglycans in the extracellular matrix?

    <p>Providing structural integrity and compressive resistance</p> Signup and view all the answers

    The secondary structure of collagen consists of which configuration?

    <p>Left-handed alpha helix</p> Signup and view all the answers

    Which molecule is known to provide compressive stiffness in the extracellular matrix?

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

    In the context of ECM components, what regulates the activities of growth factors?

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

    Study Notes

    The Extracellular Matrix (ECM)

    • Insoluble, macromolecular networks
    • Determines the shape of animals
    • Maintains positional homeostasis of organs
    • Structure and chemical makeup varies between organs
    • Not static; changes during:
      • Development/growth
      • Injury
      • Disease

    Major ECM Molecules

    • Collagens
    • Elastin
    • Proteoglycans and glycosaminoglycans (GAGs)
    • Cell adhesion molecules:
      • Fibronectin, laminin
    • ECM is ~ 65% water

    Collagens: Diversity, Structure, Biosynthesis, and Cross-Linking

    • Collagens have a unique primary, secondary, and tertiary structure.
    • Primary: Gly-X-Y repeat
    • Secondary: Left-handed alpha helix
    • Tertiary: Right-handed triple helix

    Collagen Structure

    • Three polypeptide chains (alpha chains) with repeating Gly-X-Y amino acid sequence, staggered by one residue relative to each other
    • Individual chains are left-handed helices (~1000 amino acids)
    • Three chains are wrapped around each other in a right-handed supercoiled helix

    Collagen Biosynthesis

    • Prolyl Hydroxylases
    • Lysyl Hydroxylases
    • Glycosyl Transferases
    • Lysyl Oxidase

    Tropocollagen, Fibrils and Fibers

    • Tropocollagen: ~300 nm
    • Fibrils: ~1 µm
    • Fibers: ~10 µm

    Proteoglycans and Glycosaminoglycans (GAGs)

    • GAGs are long repeating disaccharides (unbranched polysaccharides)
    • Examples of GAGs:
      • Hyaluronan
      • Keratan sulfate
      • Chondroitin sulfate
    • GAGs are negatively charged
    • They bind growth factors
    • They provide compressive stiffness
    • They can be linked to a protein to form proteoglycans (PG)

    Laminin

    • A major component of basement membranes

    ECM Life Cycle

    • Secretion
    • Activation
    • Assembly
    • Binding
    • Degradation

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    Description

    Explore the intricate details of the extracellular matrix (ECM) and the crucial role of collagens within it. This quiz focuses on the structure, biosynthesis, and functions of major ECM molecules, as well as the dynamics of ECM changes during development, injury, and disease.

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