Cell Polarity: Apical Domain Quiz
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Questions and Answers

What is the main role of microvilli in epithelial cells?

  • To facilitate communication between adjacent cells
  • To anchor the cells to the connective tissue
  • To increase the cell surface area for absorption (correct)
  • To allow for movement of the cell

    • What structural components do cilia possess?

  • Intermediate filaments
  • Actin filaments
  • Collagen fibers
  • Microtubules (correct)

    • What type of junction is always located towards the apical side of epithelial cells?

  • Adherens junctions
  • Gap junctions
  • Desmosomes
  • Tight junctions (correct)

    • Which of the following best describes the arrangement of microvilli that leads to a brush border?

    <p>Uniform, numerous, and regularly arranged</p> Signup and view all the answers

    What biochemical characteristic is essential in the connection between actin filaments in microvilli?

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

    Which type of epithelial cell modification is described as being microvilli of unusual length?

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

    What happens to microvilli in cells with less active transepithelial transport?

    <p>They become smaller and more irregularly shaped</p> Signup and view all the answers

    What cellular feature helps distinguish between the apical and basal domains in pseudostratified epithelia?

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

    What is the primary function of cadherins in adherens junctions?

    <p>Facilitate homotypic interactions between similar cells</p> Signup and view all the answers

    Which type of binding occurs when cell adhesion molecules of the same type interact?

    <p>Homotypic binding</p> Signup and view all the answers

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

    <p>To form a tight seal and prevent the migration of membrane proteins</p> Signup and view all the answers

    What role do integrins play in cellular functions?

    <p>They consist of alpha and beta glycoprotein subunits</p> Signup and view all the answers

    Which type of junction is characterized by the interaction with actin filaments?

    <p>Zonula adherens</p> Signup and view all the answers

    How do cell adhesion molecules (CAMs) affect intracellular processes?

    <p>Through connections with the cell cytoskeleton</p> Signup and view all the answers

    How do tight junctions contribute to cell polarity?

    <p>By preventing mixing of lipids between apical and lateral membranes</p> Signup and view all the answers

    Which of the following describes a characteristic of CAMs?

    <p>They participate in both homotypic and heterotypic binding</p> Signup and view all the answers

    What structure forms the primary intercellular diffusion barrier between adjacent epithelial cells?

    <p>Zonula occludens</p> Signup and view all the answers

    What is the main function of E-cadherin in epithelial cells?

    <p>Acting as a suppressor of epithelial tumor cells</p> Signup and view all the answers

    What type of junction is the zonula adherens?

    <p>A band encircling the cell</p> Signup and view all the answers

    Which junction type is primarily responsible for anchoring epithelial cells to the basement membrane?

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

    What distinguishes the paracellular transport pathway from the transcellular pathway?

    <p>Transcellular transport involves crossing both apical and basal sides</p> Signup and view all the answers

    Which cellular process is NOT directly associated with cell adhesion molecules?

    <p>Mechanical signaling</p> Signup and view all the answers

    Which of the following is NOT a component of the junctional complex in epithelial cells?

    <p>Focal adhesions</p> Signup and view all the answers

    What characteristic of the lateral domain is important for its interaction with adjacent cells?

    <p>Presence of specific cell adhesion molecules</p> Signup and view all the answers

    What role does myosin I play in the structure of microvilli?

    <p>It binds actin filaments to the plasma membrane.</p> Signup and view all the answers

    Which protein is NOT present in stereocilia?

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

    What is a distinguishing structural feature of motile cilia?

    <p>9+2 axonemal arrangement with a basal body.</p> Signup and view all the answers

    What is the main function of stereocilia?

    <p>Facilitating the absorption of substances.</p> Signup and view all the answers

    Which of the following proteins helps to stabilize the terminal web in microvilli?

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

    What is the primary role of the axoneme in cilia?

    <p>To enable movement of the cilia.</p> Signup and view all the answers

    Which type of cilia are typically found on almost all eukaryotic cells?

    <p>Primary cilia</p> Signup and view all the answers

    The internal structure of microvilli is primarily composed of which type of filament?

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

    What primary functions are regulated by integrin interactions?

    <p>Cell adhesion, movement, and shape</p> Signup and view all the answers

    Selectins are primarily involved in which process?

    <p>Mediating neutrophil migration</p> Signup and view all the answers

    Which type of junction is characterized by strong cell-to-cell attachment?

    <p>Macula adherens (spot desmosomes)</p> Signup and view all the answers

    Gap junctions primarily allow the passage of which type of molecules between cells?

    <p>Signaling molecules</p> Signup and view all the answers

    What distinguishes the immunoglobulin superfamily?

    <p>It is the largest gene family in the human genome.</p> Signup and view all the answers

    What role do hemidesmosomes play in cells?

    <p>Anchoring filaments to the basement membrane</p> Signup and view all the answers

    Which statement accurately describes focal adhesions?

    <p>They anchor actin filaments to the basement membrane.</p> Signup and view all the answers

    Which of the following best describes the function of gap junctions?

    <p>They allow direct cell-to-cell communication.</p> Signup and view all the answers

    Study Notes

    Cell Polarity: Apical Domain

    • Apical domain faces the lumen of an organ.
    • The apical membrane, facing the lumen, can have specialized structures like microvilli, stereocilia, and cilia.
    • Microvilli are finger-like projections that increase surface area for absorption.
    • Stereocilia are longer, non-motile microvilli found in some specific locations like the epididymis and sensory cells of the inner ear.
    • Cilia are hair-like projections containing microtubules, essential for movement and sensing.

    Microvilli

    • Microvilli contain a core of actin filaments and are anchored to the apical cytoplasm by a network of actin filaments called the terminal web.
    • Their number, shape, and arrangement correlate with the absorptive state of the cell.
    • Uniform, numerous, and regularly arranged microvilli form a striated border or brush border.

    Stereocilia

    • Not widely distributed, primarily found in the male reproductive system and sensory cells of the inner ear.
    • Supported by internal bundles of actin filaments, crosslinked by fimbrin.
    • Bound to the membrane by ezrin, they do not have villin.

    Cilia

    • Cilia are hair-like extensions of the apical plasma membrane containing an axoneme, a microtubule-based internal structure.
    • Axoneme extends from the basal body, a microtubule-organizing center.
    • Cilia are classified into motile cilia with a 9+2 axonemal arrangement, found in large numbers, and primary cilia, which are immotile and act as sensors.

    Cell Polarity: Lateral Domain

    • The lateral domain of epithelial cells facilitates communication and connection between adjacent cells.
    • Specialized cell adhesion molecules (CAMs) are crucial for maintaining this connection.
    • Lateral cell surface may form folds and processes, creating interdigitating margins.

    Junctional Complex

    • The junctional complex includes zonula occludens (tight junctions), zonula adherens (belt desmosomes), macula adherens (desmosomes), hemidesmosomes.
    • Tight junctions create a seal to prevent movement of lipids and specialized membrane proteins.

    Occluding Junctions

    • Tight junctions form a tight seal between adjacent cells, preventing paracellular transport and separating tissue compartments.
    • They recruit signaling molecules and link them to the actin filaments of the cell cytoskeleton.

    Zonula Adherens and Macula Adherens

    • Anchoring junctions provide lateral adhesions between epithelial cells, utilizing proteins to link into the cytoskeleton of adjacent cells.
    • Zonula adherens interact with actin filaments, while Macula Adherens interact with intermediate filaments.

    Zonula Adherens

    • A type of adherens junction linked to the actin cytoskeleton.
    • Cell adhesion molecules (CAMs) are essential for anchoring junctions.
    • CAMs control various cellular processes, including cell adhesion, proliferation, migration, and communication.

    CAMs (Cell Adhesion Molecules)

    • Four major CAMs: cadherins, integrins, selectins, and immunoglobulins.
    • Cadherins are calcium-dependent CAMs found in the zonula adherens, maintaining homotypic interactions with neighboring cells.
    • Integrins are transmembrane glycoproteins that interact with the extracellular matrix and the cytoskeleton, regulating cell adhesion, movement, and growth.
    • Selectins are expressed on white blood cells and endothelial cells, mediating cell recognition and migration.
    • Immunoglobulins are a large gene family involved in immune responses and other biological functions.

    Macula Adherens or Desmosomes

    • Strong anchoring junctions that provide direct cell-to-cell contact, anchoring intermediate filaments.
    • Localized on the lateral domain of cells and distributed in patches.

    Communicating Junctions or Gap Junctions

    • Gap junctions allow direct passage of signaling molecules between adjacent cells, facilitating communication and exchange of molecules.
    • They enable calcium movement between the cytosol of adjacent cells.

    Cell Junctions and Polarity

    • The distribution and function of different types of cell junctions play a significant role in establishing and maintaining cell polarity in epithelial tissues.

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    IDTH 201 Epithelia PDF

    Description

    Test your knowledge on the apical domain and its specialized structures, including microvilli, stereocilia, and cilia. This quiz covers the functions and features of these cellular projections, specifically their roles in absorption and sensory functions. Get ready to dive deep into cellular biology!

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