Cell Biology Junctions Quiz
38 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which component provides the primary structural strength to a layer of epithelial cells?

  • Cell-cell junctions linked to the cytoskeleton (correct)
  • The basal lamina
  • Fibrous proteins secreted by fibroblasts
  • The apical cell membrane

    • Anchoring junctions exclusively connect cells to the extracellular matrix (ECM).

    False (B)

    What type of junction is primarily responsible for creating a selectively permeable barrier between epithelial cells?

    Occluding junctions

    __________ junctions facilitate the passage of signals between adjacent cells via direct cell-cell contact.

    <p>Signal-relaying</p> Signup and view all the answers

    Match the junction type with its primary function:

    <p>Anchoring Junctions = Transmit stresses and tether to cytoskeletal filaments Occluding Junctions = Create impermeable barriers Channel-forming Junctions = Create passageways between cells Signal-relaying Junctions = Relay signals between cells</p> Signup and view all the answers

    What is the primary role of integrins as described?

    <p>Linking the actin cytoskeleton of one cell to the extracellular matrix. (D)</p> Signup and view all the answers

    Cadherins are found in all eukaryotic organisms, including fungi and plants.

    <p>False (B)</p> Signup and view all the answers

    What ion is essential for cadherin-mediated cell adhesion?

    <p>Ca2+</p> Signup and view all the answers

    The cadherin superfamily facilitates cell-cell adhesion in a manner dependent on the presence of ______ ions.

    <p>Ca2+</p> Signup and view all the answers

    Match each classical cadherin with the main tissue in which it was originally found:

    <p>E-cadherin = Epithelial cells N-cadherin = Nerve cells P-cadherin = Cells of the placenta</p> Signup and view all the answers

    Which type of junction is primarily responsible for preventing leakage between epithelial cells?

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

    Gap junctions are typically found on the apical side of the cell, above tight junctions.

    <p>False (B)</p> Signup and view all the answers

    What is the main function of channel-forming junctions like gap junctions?

    <p>transfer of small molecules like ions</p> Signup and view all the answers

    In the Notch/Delta pathway, a membrane-bound ______ on one cell interacts with a membrane-bound receptor on another cell to transmit a signal.

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

    Which cytoskeletal filaments are typically anchored between two cells at anchoring junctions?

    <p>Actin filaments and intermediate filaments (D)</p> Signup and view all the answers

    Hemidesmosomes connect two cells to each other.

    <p>False (B)</p> Signup and view all the answers

    What role do cadherins play in cell-cell adhesion?

    <p>Mediating attachment of cell to cell (A)</p> Signup and view all the answers

    Which of the following components primarily bear the mechanical stress in connective tissues like bone and tendon?

    <p>Collagen-rich extracellular matrix (D)</p> Signup and view all the answers

    Epithelial tissues primarily rely on the extracellular matrix for strength and bearing mechanical stress.

    <p>False (B)</p> Signup and view all the answers

    What is the main function of FAK in the context of integrin connections?

    <p>breaking integrin connections</p> Signup and view all the answers

    The RGD domain is a key recognition sequence found on ______ that interacts with integrins.

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

    Match the following terms with their description:

    <p>Integrins = Transmembrane receptors that mediate cell-ECM interactions. Anchorage Dependence = The requirement for cell attachment to a substrate for survival and growth. FAK = A protein tyrosine kinase involved in focal adhesion dynamics. Velcro Principle = The concept that multiple weak interactions can create strong adhesion.</p> Signup and view all the answers

    Which of the following is an accurate description of how animal cells combine into strong, stable structures?

    <p>The strength of the ECM and cell-cell adhesions linking cytoskeletons provide strength. (D)</p> Signup and view all the answers

    Hemichannels are typically kept in an open conformation to facilitate constant communication between cells.

    <p>False (B)</p> Signup and view all the answers

    What is the primary function of cell-cell junctions and cell adhesion?

    <p>To hold cells together and control the orientation of internal structures. (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the role of cadherins in cell adhesion and signaling?

    <p>Cadherins mediate cell adhesion and can also relay information to the cell interior through signaling functions. (C)</p> Signup and view all the answers

    E-cadherin is the only type of cadherin found on epithelial cells.

    <p>False (B)</p> Signup and view all the answers

    Why is the shift in relative abundance of different cadherins important for cells?

    <p>Differentiation and organization</p> Signup and view all the answers

    Cadherins mediate ______ adhesion, meaning they bind to the same type of cadherin on another cell.

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

    What is the role of Calcium (Ca2+) in cadherin function?

    <p>Ca2+ is needed to lock the hinge region and promote a rigid structure. (B)</p> Signup and view all the answers

    What is the primary role of desmosome junctions in epithelial cells?

    <p>Providing mechanical strength. (A)</p> Signup and view all the answers

    Desmosomes create a belt-like structure across cells, similar to adherens junctions.

    <p>False (B)</p> Signup and view all the answers

    In heart muscle cells, desmosomes attach to __________ filaments.

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

    Which type of cellular filament is linked to adherens junctions?

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

    How do cadherins facilitate cell-cell interactions?

    <p>Cadherins bind to cadherin molecules of the same subtype on adjacent cells.</p> Signup and view all the answers

    What is the role of WNT signaling in the context of cadherins and cell junctions?

    <p>It activates genes involved with cadherins. (A)</p> Signup and view all the answers

    Match the cell junction with its corresponding attached cytoskeletal filament:

    <p>Desmosomes (heart muscle cells) = Desmin Adherens junctions = Actin Desmosomes (epithelial cells) = Keratin</p> Signup and view all the answers

    Which of the following best describes the 'Velcro principle' in the context of cell junctions?

    <p>The means by which linking structures connect to another cell. (C)</p> Signup and view all the answers

    Flashcards

    Collagen

    A protein that provides structural support in tissues.

    Elastin

    A protein that allows tissues to resume shape after stretching.

    Integrins

    Proteins that facilitate cell-ECM adhesion and signal transduction.

    RGD domain

    A sequence in proteins that interacts with integrins.

    Signup and view all the flashcards

    FAK (Focal Adhesion Kinase)

    An enzyme that helps regulate cell adhesion and signaling.

    Signup and view all the flashcards

    Cell junctions

    Structures that link cells together in tissues.

    Signup and view all the flashcards

    Anchorage dependence

    The requirement for cells to attach to ECM to grow.

    Signup and view all the flashcards

    Connective tissues

    Tissues that provide support and bind other tissues; rich in ECM.

    Signup and view all the flashcards

    Integrin superfamily

    A group of proteins that mediate cell attachment to the extracellular matrix.

    Signup and view all the flashcards

    Desmosomes

    Special structures that mediate cell adhesion using cadherins.

    Signup and view all the flashcards

    Cadherins

    Proteins that enable Ca2+-dependent cell-cell adhesion in animals.

    Signup and view all the flashcards

    E-cadherin

    A type of cadherin found predominantly in epithelial cells.

    Signup and view all the flashcards

    Ca2+ ions

    Ions essential for cadherin function and cell adhesion.

    Signup and view all the flashcards

    Extracellular Matrix (ECM)

    A thin layer mainly consisting of a basal lamina that provides structural support to tissues.

    Signup and view all the flashcards

    Epithelial Cells

    Cells that line surfaces and are polarized with an apical side facing outward and a basal side attached to the ECM.

    Signup and view all the flashcards

    Anchoring Junctions

    Junctions that link cells to each other and to the ECM, allowing stresses to be transmitted through the cytoskeleton.

    Signup and view all the flashcards

    Occluding Junctions

    Cell junctions that seal gaps between epithelial cells to create impermeable or selectively permeable barriers.

    Signup and view all the flashcards

    Gap Junctions

    Junctions that create channels linking the cytoplasm of adjacent cells for communication.

    Signup and view all the flashcards

    Homophilic adhesion

    Adhesion between identical cadherins on adjacent cells.

    Signup and view all the flashcards

    Calcium dependence

    The requirement of calcium ions (Ca2+) for cadherin structural stability.

    Signup and view all the flashcards

    Junction symmetry

    The property where anchoring junctions link identical structures in both cells involved.

    Signup and view all the flashcards

    Tight Junctions

    Occluding junctions that prevent leakage between epithelial cells.

    Signup and view all the flashcards

    Notch/Delta Pathway

    Signal relaying junction where a ligand interacts with a receptor on adjacent cells.

    Signup and view all the flashcards

    Adherens Junctions

    Junctions that connect the actin cytoskeleton between two cells.

    Signup and view all the flashcards

    Hemidesmosomes

    Anchor cells to the extracellular matrix using intermediate filaments.

    Signup and view all the flashcards

    Integrin Signaling

    Links actin filaments to the extracellular matrix at the basal side of epithelial cells.

    Signup and view all the flashcards

    β-catenin

    A protein that links cadherins to the actin cytoskeleton in cell junctions.

    Signup and view all the flashcards

    Intermediate filaments

    Cytoskeletal components that provide tensile strength and stability to cells.

    Signup and view all the flashcards

    Mechanical strength in epithelium

    Desmosomes give epithelial tissues their durability and resistance to stress.

    Signup and view all the flashcards

    WNT signaling

    A pathway that activates genes for cadherins, enhancing cell adhesion.

    Signup and view all the flashcards

    Velcro principle

    Refers to the way certain cell junctions link cells together like Velcro.

    Signup and view all the flashcards

    Study Notes

    Keywords from Lecture 7

    • Collagen and elastin
    • Fibronectin
    • RGD domain
    • Integrins
    • Outside-in and inside-out signaling
    • FAK
    • Velcro Principle
    • Anchorage dependence

    Hemichannels

    • Are hemichannels usually kept in the closed or open conformation?
    • Many integrin connections (focal adhesions) need to be able to make and break.
    • FAK is responsible for breaking them.

    Lecture 8

    • Cell junctions, cell adhesion, and the ECM

    Cell Interactions

    • Interactions between cells in multicellular organisms are fundamental.
    • Cells connect to each other through cell-cell junctions or the ECM.
    • Attachments to other cells and ECM control cell orientation.
    • Defects in cell junctions, cell adhesion, and ECM underlie many diseases.

    Cell Structure

    • Small motile cells filled with aqueous medium and enclosed in plasma membrane.
    • Two basic building strategies:
      • Strength of the ECM
      • Strength of the cytoskeleton within the cell along with cell-cell adhesions that link cytoskeletons of neighboring cells.
      • Cytoskeleton of one cell is linked to the cytoskeleton of the neighboring cell which provides strength.

    Animal Tissues

    • Animal tissues are varied but can be classified into:
      • Connective tissues (e.g., bone, tendon)
        • Abundant ECM, sparse cells
        • Matrix (rich in fibrous polymers like collagen) bears mechanical stress.
      • Epithelial tissues (e.g., lining of gut, skin)
        • Cells closely bound together into sheets.
        • Scarce ECM, mainly a thin basal lamina.
        • Cells linked via cell-cell adhesion; stress is dispersed this way.

    Cell Junctions

    • Physical attachment is crucial.
    • Junctions between cell-cell or cell-matrix are structurally diverse.
    • Four main functions can be distinguished, each on a molecular basis.

    Types of Cell Junctions

    • Anchoring junctions:
      • Both cell-cell and cell-matrix adhesions
      • Transmit stresses, linked to cytoskeletal filaments
    • Occluding junctions:
      • Seal gaps in epithelia, creating impermeable or selectively permeable barriers.
    • Channel-forming junctions:
      • Create passageways connecting adjacent cell cytoplasms.
    • Signal-relaying junctions:
      • Allow signal relay across plasma membranes at cell-cell contact sites.

    Anchoring Junctions (Details)

    • Anchor cells to each other and the ECM.
    • Intermediate filaments, oriented toward the basal side, connect to basal lamina or other adjacent cells.
    • Tight junctions: Located primarily at the apical surface of cells. Prevent leakage through the epithelial layer.
    • Channel-forming junction (e.g., gap junctions): Found usually closer to the basal side of cells or beneath tight junctions. Allow transfer of small molecules like ions between cells.
    • Signal relaying junctions (e.g., Notch/Delta pathway): Ligand on one cell interacts with a receptor on another cell, transmitting a signal to both cells.

    Cadherins

    • Cadherins mediate Ca2+-dependent cell-cell adhesion.
    • Present in all multicellular animals but absent in fungi, plants, bacteria, and archaea.
    • Their adhesive functions are complemented by signaling functions to relay information internally to the cell.
    • Several types, named according to the tissue where they're found (E-cadherin, N-cadherin, P-cadherin).
    • Their affinity for partners is relatively low but strength is high due to many weak bonds.
    • Homophilic binding (like binds to like): This specificity is essential for tissue organization.
    • Calcium (Ca2+) is critical to the binding of cadherins.
    • Cell-cell adhesions are mediated by cadherins at junctions - these are called adherens junctions.
    • Actin cytoskeleton linked between the two cells

    Cell Segregation

    • Cadherins are essential for cell sorting/segregation.
    • Dissociated cells from different embryonic vertebrate organs (like liver, retina) will re-assemble into tissues of origin.
    • Selective expression and regulation of different cadherins leads to different cell types

    Cell-Cell Junctions (Summary)

    • Critical for modeling the shapes of multicellular structures.
    • Example: Adherens junctions form a continuous adhesion belt in epithelia.
    • Junctions send signals, affecting cell differentiation (making large changes to their internal affairs).
    • Complex crosstalk between adhesion machinery and chemical signaling pathways (e.g., β-catenin signaling, Wnt signaling).
    • Desomosomes give epithelia mechanical strength. Structurally similar to adherens junctions but link to intermediate filaments (keratin in epithelial cells, desmin in heart muscle cells).

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Lecture 8 2025 Cell Junctions PDF

    Description

    Test your knowledge on the various types of cell junctions and their functions in epithelial tissues. This quiz covers anchoring junctions, cadherins, integrins, and gap junctions. Understanding the role of these components is essential for grasping the principles of cellular adhesion and communication.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser