Microfilaments and Cytoskeleton Quiz
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Questions and Answers

What is the cytoskeleton?

  • A simple protein
  • Only found in plant cells
  • A type of lipid structure
  • A complex network of protein filaments that traverse the cell cytoplasm (correct)

    • What protein is used to create microfilaments?

    Actin

    What are intermediate filaments primarily used for?

    Mechanical strength

    What are microtubules made of?

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

    What is the role of myosin II?

    <p>Contractile strength in muscles</p> Signup and view all the answers

    Myosin I functions in vesicle transport.

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

    Which of the following describes treadmilling?

    <p>Addition of G-actin to the plus end while removing from the minus end</p> Signup and view all the answers

    What do actin-binding proteins do?

    <p>Help regulate actin binding states</p> Signup and view all the answers

    What is the function of spectrin?

    <p>Attach sides of filaments to the plasma membrane</p> Signup and view all the answers

    Which protein is involved in the bundling of actin filaments?

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

    What is gelsolin sensitive to?

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

    Thymosin promotes the polymerization of G-actin.

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

    What does profilin do?

    <p>Catalyzes ATP-ADP exchange</p> Signup and view all the answers

    What links spectrin to the cytoplasmic domain of band 3?

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

    Hereditary spherocytosis is caused by a mutation in actin.

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

    What type of cells do microvilli increase surface area for?

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

    Study Notes

    Cytoskeleton and Its Composition

    • The cytoskeleton is a protein filament network within the cell's cytoplasm, crucial for structure and function.
    • Microfilaments are primarily composed of actin, providing flexibility and a dynamic structure.
    • Intermediate filaments consist of proteins like vimentin and lamin, offering mechanical strength without flexibility.
    • Microtubules are large, tubulin-based structures that provide support and shape to the cell.

    Actin Filaments and Their Characteristics

    • Microfilaments, made of actin and myosin, facilitate various cellular processes including plasma membrane movement.
    • F-actin is filamentous actin, while G-actin refers to monomeric actin units; two G-actin molecules form F-actin.
    • Actin filaments exhibit polarity, with a slow-growing minus end and a fast-growing plus end.

    Actin Dynamics

    • Treadmilling describes the process where G-actin is added to the plus end of a filament and simultaneously removed from the minus end, essential for maintaining filament length.
    • ATP-bound G-actin is necessary for polymerization into actin filaments.

    Regulation by Actin-Binding Proteins

    • Various proteins regulate actin dynamics:
      • Thymosin prevents G-actin polymerization, maintaining a pool of monomers.
      • Profilin facilitates ATP-ADP exchange on actin, promoting filament formation.
      • Gelsolin caps the plus end of filaments and can sever them, playing a role in cellular motility.
      • Cytochalasins inhibit actin polymerization, halting cell movement.
      • Phalloidins bind tightly to actin filaments, preventing depolymerization.

    Spectrin and Cell Structure Maintenance

    • Spectrin anchors actin filaments to the cell membrane, essential for maintaining the shape of red blood cells.
    • Junctional complexes involve spectrin tetramers linked with short actin filaments.
    • Ankyrin connects spectrin to membrane proteins, such as band 3, and helps stabilize the connection between membrane and cytoskeleton.
    • Hereditary spherocytosis results from mutations in ankyrin, causing spherical red blood cells.
    • Hereditary elliptocytosis is linked to spectrin mutations that lead to elliptical red blood cells.
    • Sickle cell anemia is associated with issues in actin modifications, causing aggregated forms that disrupt normal cell function.

    Structural Components of Epithelial Cells

    • Microvilli, found on epithelial cells' apical surfaces, enhance surface area and consist of actin filaments bundled by fimbrin and villin.
    • The terminal web is a network of actin and associated proteins anchored to the plasma membrane, contributing to cell stability.

    Dystrophin and Muscle Function

    • Dystrophin is a crucial protein in skeletal muscles, anchoring actin filaments to cell membranes and associated with muscular dystrophy.

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    Description

    Test your knowledge on microfilaments, actin, and the cytoskeleton. This quiz covers essential definitions and roles of different filament types within the cell. Perfect for those studying cell biology and related topics.

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