Cytoskeleton and Filaments Quiz
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Questions and Answers

What is the primary role of microtubules in nerve cells?

  • Facilitating cell apoptosis
  • Maintaining and stabilizing the shape of the cell (correct)
  • Production of neurotransmitters
  • Regulation of blood flow

    • What structural feature is unique to centrioles?

  • Formed of actin filaments
  • Always found in every cell type
  • Made exclusively of collagen fibers
  • Consist of 27 microtubules arranged in triplets (correct)

    • How do cytotoxic drugs like colchicine affect microtubules?

  • They enhance the formation of new microtubules
  • They stabilize existing microtubules
  • They prevent the formation of new microtubules (correct)
  • They increase the diameter of microtubules

    • Which of the following is NOT a function of microtubules?

    <p>Production of ATP</p> Signup and view all the answers

    What structural characteristic do microtubules possess?

    <p>They are non-branching and hollow tubules</p> Signup and view all the answers

    During which phase of the cell cycle do cells contain two pairs of centrioles?

    <p>G2 phase</p> Signup and view all the answers

    What is a primary function of glial cells in contrast to nerve cells?

    <p>Supporting and maintaining cell shape</p> Signup and view all the answers

    What are microtubule organizing centers (MTOCs) responsible for?

    <p>Initiating the polymerization of microtubules</p> Signup and view all the answers

    Which of the following cell organelles is considered non-membranous?

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

    What is the primary role of microtubules within the cytoskeleton?

    <p>To facilitate cell shape and movement</p> Signup and view all the answers

    Which type of filament is associated with muscle contraction?

    <p>Thick filaments</p> Signup and view all the answers

    What is the approximate diameter of microfilaments?

    <p>6 nm</p> Signup and view all the answers

    Intermediate filaments are classified based on which of the following characteristics?

    <p>Their diameter</p> Signup and view all the answers

    Which of the following is NOT a characteristic of cytoplasmic filaments?

    <p>They are always surrounded by a membrane</p> Signup and view all the answers

    Which of the following types of filaments cannot produce contraction?

    <p>Intermediate filaments</p> Signup and view all the answers

    What role do thin filaments play in amoeboid movement?

    <p>They contract to propel the cell</p> Signup and view all the answers

    What is the primary function of cilia?

    <p>To move secretions or particles over the tissue surface.</p> Signup and view all the answers

    What structural feature distinguishes flagella from cilia?

    <p>Flagella have a whip-like movement and are much longer than cilia.</p> Signup and view all the answers

    Which structure is responsible for anchoring the basal body of a cilium?

    <p>Rootletin protein.</p> Signup and view all the answers

    What is found in the structure of a cilium?

    <p>Nine doublets and two central single microtubules.</p> Signup and view all the answers

    Which protein is associated with the arms that arise from the subunit-A of a cilia?

    <p>Dynein.</p> Signup and view all the answers

    Which of the following statements about cilia is incorrect?

    <p>Cilia consist only of microtubules.</p> Signup and view all the answers

    What type of movement do flagella exhibit?

    <p>Whip-like.</p> Signup and view all the answers

    Cilia are primarily involved in which of the following systems?

    <p>Respiratory system.</p> Signup and view all the answers

    What is the structural composition of a centriole?

    <p>27 microtubules arranged in triplets</p> Signup and view all the answers

    Which process can be inhibited by cytotoxic drugs like colchicine?

    <p>Formation of new microtubules</p> Signup and view all the answers

    In which phases of the cell cycle does a cell contain only one pair of centrioles?

    <p>G1 phase</p> Signup and view all the answers

    What role do microtubules play in cell division?

    <p>Create the mitotic spindle</p> Signup and view all the answers

    Which of the following structures is indicative of a microtubule's structural properties?

    <p>Hollow tubes with a fixed diameter of 25 nm</p> Signup and view all the answers

    Where are microtubule organizing centers (MTOCs) primarily located?

    <p>Near the centrosome</p> Signup and view all the answers

    Which function is associated with glial cells in the context of nerve cells?

    <p>Support and maintain cell shape</p> Signup and view all the answers

    What experimental technique would be employed to visualize microtubules in light microscopy?

    <p>Fluorescent tagging with a specific dye</p> Signup and view all the answers

    What is the primary component of thin filaments?

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

    Which of the following diameters corresponds to intermediate filaments?

    <p>8-10 nm</p> Signup and view all the answers

    Which of the following non-membranous organelles does NOT play a role in muscle contraction?

    <p>Intermediate filaments</p> Signup and view all the answers

    What is the function of microtubules in motile cells?

    <p>Facilitating amoeboid movement</p> Signup and view all the answers

    Which type of cell structure is characterized as a component of the cytoskeleton but does not have a defined unit membrane?

    <p>Cytoplasmic filaments</p> Signup and view all the answers

    Which of the following statements is true regarding thick filaments?

    <p>They are known for their ability to contribute to muscle contraction.</p> Signup and view all the answers

    What is the essential role of tropomyosin in muscle contraction?

    <p>Regulating interactions between actin and myosin</p> Signup and view all the answers

    Which of the following is categorized as a part of the cytoskeleton?

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

    What is the primary structural characteristic that distinguishes cilia from flagella?

    <p>Cilia typically have a shorter length compared to flagella.</p> Signup and view all the answers

    What role does the protein dynein play in the structure of cilia?

    <p>It contributes to the wave-like movement of cilia.</p> Signup and view all the answers

    Which of the following accurately describes the composition of the basal body in cilia?

    <p>Similar in structure to a centriole with nine triplets.</p> Signup and view all the answers

    How do the movements of cilia function in the respiratory system?

    <p>They wave to move secretions along the surface.</p> Signup and view all the answers

    Which component of cilia connects subunit-A and subunit-B of adjacent doublets?

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

    What function do the rootlets serve in the structure of cilia?

    <p>They anchor the basal body to surrounding cytoplasm.</p> Signup and view all the answers

    What is a distinguishing characteristic of a flagellum compared to a cilium?

    <p>Flagella produce a whip-like swimming movement.</p> Signup and view all the answers

    Which of the following statements regarding the microtubule structure of cilia is correct?

    <p>Each cilium consists of 9 doublets and 2 central single microtubules.</p> Signup and view all the answers

    Study Notes

    Cytoskeleton

    • A type of cell organelle not surrounded by a unit membrane.
    • Plays an important role as the cell's internal framework.
    • Composed of cytoplasmic filaments (6-16nm in diameter) and microtubules (25 nm in diameter).

    Cytoplasmic Filaments

    • Thread-like structures that are part of the cytoskeleton.
    • Only visible when present in bundles under special stains (silver).
    • Classified into thin filaments, intermediate filaments, and thick filaments.

    Thin Filaments (Microfilaments)

    • Composed of actin with tropomyosin and troponin.
    • Involved in muscle contraction with myosin.
    • Found in microvilli for movement.
    • Involved in amoeboid movement of motile cells.
    • Involved in the formation of the cleavage furrow during cell division.
    • Found in blood platelets for clot retraction.

    Thick Filaments (Myosin)

    • Diameter of 12-16 nm (thicker than myosin).
    • Found in muscle in association with actin filaments, forming myofibrils for contraction.

    Intermediate Filaments

    • Diameter of 8-10 nm.
    • Over 50 types can be identified using immunocytochemical techniques.
    • Not capable of producing contraction.
    • Found in muscle, epithelial cells, connective tissue, muscle, nerve cells, and glial cells.
    • Play a major role in supporting and maintaining the shape of cells.
    • Important for adhesion between epithelial cells, allowing them to withstand harsh treatments.
    • Used for tumor identification.

    Microtubules

    • Non-branching, hollow tubules of variable length but fixed diameter.
    • Composed of tubulin protein (in free dimeric or polymerized forms).
    • Polymerization is directed by microtubule organizing centers (MTOCs), which include centrioles and centromeres of chromosomes.
    • Difficult to see with light microscopy except using special stains.
    • Appear as tiny circles, 25 nm in diameter, under electron microscopy.
    • The wall consists of 13 protofilaments composed of tubulin dimers.
    • The length of microtubules can be changed by adding or removing tubulin molecules at their end.

    Functions of Microtubules

    • Maintain and stabilize the shape of the cell.
    • Intracellular transport.
    • Formation of the mitotic spindle during cell division.
    • Structure of cilia, flagella, and centrioles.

    Centrioles

    • Derived from microtubules.
    • Responsible for cell division, so they are absent in non-dividing cells such as red blood cells and nerve cells.
    • Typically present near the nucleus in an area called the centrosome.
    • Not demonstrable with H&E stain; appear dark blue with iron hematoxylin stain under light microscopy.
    • A cell has a single pair of centrioles during G1 of the cell cycle.
    • A cell has two pairs of centrioles during G2 of the cell cycle.
    • Two short, hollow cylinders perpendicular to each other.
    • The wall of each centriole is formed by 27 microtubules arranged longitudinally into 9 bundles, each bundle consisting of 3 microtubules (triplets).

    Functions of Centrioles

    • Participate in the formation of the mitotic spindle during cell division.
    • Involved in the formation of cilia and flagella.

    Cilia

    • Motile, hair-like processes projecting over the cell surface, capable of moving fluids and particles along the surface in one direction.
    • Appear as short, fine, hair-like structures arising from the free surface of the cell, with hundreds per cell.
    • The cytoplasm of the cell underneath them appears refractile and densely stained.
    • Each cilium consists of a shaft, basal body, and rootlets.
    • Finger-like projection over the cell surface covered by the cell membrane.
    • Contains 9 doublets and 2 central single microtubules.
    • The microtubules of the nine doublets are formed of subunit-A (complete) and subunit-B (incomplete).
    • The microtubules of the singlets are complete.
    • Two arms arise from subunit-A formed of a protein dynein and have ATPase activity.
    • There are connections between subunit-A and subunit-B of adjacent doublet called nexin.
    • The basal body is similar to the centriole in structure, formed of nine triplets, longitudinally arranged protofilaments, containing rootletin protein, which anchors the basal body to the surrounding cytoplasm.

    Functions of Cilia

    • Move in a wave-like manner to move secretions or particles over the tissue surface, for example, in the respiratory system and female genital system.
    • Can act as receptors for receiving light.

    Flagella

    • Cytoplasmic processes, for example, the tail of a spermatozoan.
    • Similar to cilia, having 9 peripheral doublets of micro-tubules and two central singlets.
    • Much longer than cilia (~200 um).
    • Each outer doublet has a large outer fiber, which is absent in cilia.
    • Whip-like swimming movement.

    Cytoskeleton

    • A type of cell organelle not surrounded by a unit membrane.
    • Comprises cytoplasmic filaments and microtubules.
    • Important for cell shape and structure.

    Cytoplasmic Filaments

    • Thread-like structures that act as part of the cytoskeleton within cells.
    • Only visible in bundles by special staining using silver.
    • Classified based on their diameter: thin filaments (microfilaments), intermediate filaments, and thick filaments.

    Thin filaments

    • Also known as microfilaments
    • Composed of actin, tropomyosin, and troponin.
    • Play roles in muscle contraction with myosin, movement of microvilli, amoeboid movement, formation of the cleavage furrow during cell division, and clot retraction in blood platelets.

    Thick filaments

    • Also known as myosin
    • Diameter: 12-16 nm (thicker than actin)
    • Found in muscle cells alongside actin filaments, forming myofibrils responsible for contraction.

    Intermediate filaments

    • Diameter: 8-10 nm
    • Around 50 different types that can be identified using immunocytochemical techniques.
    • Don't actively produce contraction.
    • Important for supporting and maintaining cell shape, cell adhesion in epithelial tissues to withstand harsh treatments, and tumor identification.

    Microtubules

    • Non-branching, hollow tubules with varying lengths, but a fixed diameter.
    • Composed of the protein tubulin, which can exist in free dimeric or polymerized forms.
    • Tubulin dimers can polymerize into microtubules, a process directed by microtubule organizing centers (MTOCs)
    • MTOCs include centrioles and centromeres of chromosomes.
    • Difficult to see under a light microscope (L/M) unless special stains are used.
    • Visible as tiny circles (25 nm in diameter) under an electron microscope (E/M).
    • Their walls consist of 13 protofilaments of tubulin dimers.
    • Their length is dynamic, increasing or decreasing by adding or removing tubulin molecules at their ends.

    Microtubule Functions

    • Maintaining and stabilizing cell shape.
    • Performing intracellular transport.
    • Forming the mitotic spindle during cell division.
    • Structuring cilia, flagella, and centrioles.

    Centrioles

    • Derived from microtubules
    • Responsible for cell division, so absent in non-dividing cells like red blood cells (RBCs) and nerve cells.
    • Located near the nucleus in a region called the centrosome.
    • Visible as dark blue under an iron hematoxylin stain (L/M) but not under a hematoxylin and eosin (H&E) stain.
    • Cells usually have a single pair of centrioles during the G1 stage of the cell cycle, but two pairs during the G2 stage.
    • Appear as two short, hollow cylinders perpendicular to each other.
    • Each centriole wall is composed of 27 microtubules arranged longitudinally in nine bundles, with each bundle containing three microtubules (triplets) under an electron microscope (E/M).

    Centriole Functions

    • Forming the mitotic spindle during cell division.
    • Responsible for the formation of cilia and flagella.

    Cilia

    • Motile hair-like processes projecting from the cell surface that move fluids and particles in one direction.
    • Visible as short, fine, hair-like structures arising from the free surface of the cell, often hundreds per cell.
    • The cytoplasm beneath cilia appears refractile and densely stained.
    • Each cilium consists of a shaft, basal body, and rootlets.
    • Finger-like projections from the cell surface covered by the cell membrane.
    • Contains 9 doublets and 2 central single microtubules.
    • The microtubules of the nine doublets are formed of a complete subunit-A and an incomplete subunit-B.
    • The central single microtubules are complete.
    • Two arms arise from subunit-A, composed of the protein dynein with ATPase activity.
    • Connections between subunit-A and subunit-B of adjacent doublets are called nexin.

    Basal Body of Cilia

    • Similar in structure to a centriole, composed of nine triplets.
    • Formed of longitudinally arranged protofilaments containing rootletin protein, which anchors the basal body to the surrounding cytoplasm.

    Cilium Function:

    • Cilia move in a wave-like manner to move cellular secretions or particles across a tissue surface. Examples include the respiratory and female genital systems.
    • Cilia can function as receptors for receiving light.
    • Flagellum: a long cilium that forms the tail of sperm, facilitating motility.

    Flagella

    • Cytoplasmic processes like the tail of a spermatozoon.
    • Similar to cilia, with 9 peripheral doublets of microtubules and two central singlets.
    • Much longer than cilia (200 µm).
    • Each outer doublet has a large outer fiber, which is absent in cilia.
    • Show a whip-like swimming movement.

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    Description

    Test your knowledge on the cytoskeleton, its composition, and the types of filaments it contains. Explore the roles of microfilaments, thick filaments, and their significance in muscle contraction and cell movement. This quiz covers essential concepts related to cell structure and function.

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