Cellular Biology I: Cell Interactions
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Questions and Answers

What are focal adhesions primarily responsible for?

  • Transmitting electrical signals between cells
  • Connecting two neighboring cells
  • Adhering cells to the extracellular matrix (correct)
  • Providing structural support to tissues

    • Which type of junctional complex is involved in cell-substrate anchorage?

  • Adherens junctions
  • Focal adhesions (correct)
  • Tight junctions
  • Gap junctions

    • How do cells utilize integrins in focal adhesions?

  • To form tight junctions with adjacent cells
  • To regulate gene expression within the nucleus
  • To adhere to pathogens and bacteria
  • To interact with the extracellular environment and transduce mechanical signals (correct)

    • What is the primary function of tight junctions in epithelial cells?

    <p>Create a barrier to maintain cell polarity</p> Signup and view all the answers

    What is a key feature of hemidesmosomes compared to focal adhesions?

    <p>They anchor cells to the extracellular matrix without transmitting signals</p> Signup and view all the answers

    Which protein family plays a significant role in sealing the paracellular space of tight junctions?

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

    What happens to actin filaments during mechanical signal transduction at focal adhesions?

    <p>They undergo contraction</p> Signup and view all the answers

    What is the function of connexones in gap junctions?

    <p>Connect the cytoplasms of adjacent cells</p> Signup and view all the answers

    Which type of junction is specifically characterized by discrete sites of cell adhesion?

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

    Which of the following proteins is involved in the regulation of paracellular permeability in tight junctions?

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

    What type of signaling is transmitted through focal adhesions?

    <p>Mechanical signals in both directions</p> Signup and view all the answers

    What type of junction is primarily responsible for the synchronous contraction of cardiac muscle cells?

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

    What distinguishes hemidesmosomes from focal adhesions?

    <p>Hemidesmosomes are formed exclusively in epithelial cells</p> Signup and view all the answers

    What role do focal adhesions serve in relation to the ECM?

    <p>They provide mechanical linkage and biochemical signaling.</p> Signup and view all the answers

    Which proteins are primarily involved in connecting integrins to actin filaments?

    <p>Talin, actinin, and vinculin</p> Signup and view all the answers

    What initiates the clustering of integrins at the cell surface?

    <p>Conformational changes induced by ECM binding</p> Signup and view all the answers

    What effect does the attachment of integrins to ECM ligands have on protein kinases?

    <p>It activates them and triggers signaling pathways.</p> Signup and view all the answers

    How does talin facilitate the formation of focal adhesions?

    <p>By undergoing a conformational change to expose binding sites.</p> Signup and view all the answers

    What is the function of myosin in relation to actin filaments during focal adhesion?

    <p>It generates traction forces at cell-substrate attachment points.</p> Signup and view all the answers

    What characterizes hemidesmosomes in cellular structure?

    <p>They are discrete sites connecting cells to the basement membrane.</p> Signup and view all the answers

    Which of the following accurately describes the composition of focal adhesions?

    <p>Macromolecular assemblies enriched in integrins.</p> Signup and view all the answers

    What happens to talin once integrins bind to ECM components?

    <p>It undergoes changes that enhance actin binding and activation.</p> Signup and view all the answers

    What is the primary function of cadherins within the zonula adherens?

    <p>Facilitating homophilic interactions between identical extracellular domains</p> Signup and view all the answers

    Which of the following components is NOT associated with macula adherens junctions?

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

    What type of interactions do desmogleins and desmocollins mediate in macula adherens?

    <p>Heterophilic interactions</p> Signup and view all the answers

    Which protein indirectly binds cadherins via beta-catenin in zonula adherens?

    <p>Alpha-catenin</p> Signup and view all the answers

    In which type of tissue would you most likely find macula adherens junctions?

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

    What is the primary structural characteristic of zonula adherens junctions?

    <p>Belt-shaped junctions encircling each cell</p> Signup and view all the answers

    Which of the following best describes the arrangement of macula adherens junctions?

    <p>Randomly arranged on lateral sides of plasma membranes</p> Signup and view all the answers

    How do cadherins facilitate cell-cell adhesion?

    <p>Through homophilic interactions between identical extracellular domains</p> Signup and view all the answers

    Which protein is known as delta catenin and plays a role in the zonula adherens?

    <p>P120 catenin</p> Signup and view all the answers

    Which type of intermediate proteins links the cytoplasmic domains of desmosomes to intermediate filaments?

    <p>Linker proteins</p> Signup and view all the answers

    What leads to the detachment of the lower layer of the epidermis in bullous pemphigoid?

    <p>Production of auto-antibodies against hemidesmosome proteins</p> Signup and view all the answers

    What is a primary characteristic of epidermolysis bullosa?

    <p>Mutations affecting hemidesmosome function</p> Signup and view all the answers

    Which junction is primarily responsible for Ca2+-mediated cell adhesion?

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

    Which statement about adherens junctions is true?

    <p>They are involved in linking adjacent cells via cadherin proteins.</p> Signup and view all the answers

    Which protein family is NOT part of the cadherin superfamily?

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

    What function do cadherin repeats serve in adherens junctions?

    <p>Binding Ca2+ ions for cell adhesion</p> Signup and view all the answers

    What is a major outcome of the auto-antibodies produced in bullous pemphigoid?

    <p>Severe blistering of the skin</p> Signup and view all the answers

    Which of the following best describes the structure of hemidesmosomes?

    <p>They link the cytoskeleton to the extracellular matrix.</p> Signup and view all the answers

    What type of connection does a tight junction provide between cells?

    <p>Barrier to diffusion</p> Signup and view all the answers

    Which of the following types of junctions is categorized as part of cell-cell junctions?

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

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    Cellular Biology I - Course Information

    • Instructor: Prof. Wanda Lattanzi
    • Department: Life Science and Public Health, Section of Biology
    • Room: 352bis
    • Location: 1st Floor Istituti Biologici
    • Email: [email protected]

    Cell-Cell and Cell-Substrate Interactions

    •  Images show different types of cell-cell junctions: adherens junctions, gap junctions, tight junctions, desmosomes, and hemidesmosomes.
    • These structures enable cells to interact with each other and with the extracellular matrix.

    Cell-Substrate Anchorage - Focal Adhesions

    • Cells adhere to the substrate through focal adhesions (FAs).
    • Focal adhesions are discrete sites on the cell surface that allow the cell to adhere to the substrate and sense the external environment.
    • These sites are crucial for cell locomotion and signal transduction.

    Cell-Substrate Anchorage - Hemidesmosomes

    •  Hemidesmosomes are specific structures that mediate cell adhesion to the extracellular matrix (ECM), particularly to the basement membrane.
    • Hemidesmosomes are crucial for cell attachment and structural integrity, especially in tissues subject to mechanical stress.
    • Proteins like BP180 are integral parts of these junctions.

    Hemidesmosomes in Human Diseases

    •  Autoimmune disorders like bullous pemphigoid involve the production of antibodies targeting hemidesmosome proteins, leading to skin blistering.
    • Genetic mutations in proteins associated with hemidesmosomes (like keratin, plectin, etc.) can cause epidermolysis bullosa, a condition characterized by skin fragility and blistering.

    Cell-Cell Junctions

    • Adherens Junctions: Mediated by cadherins; form a belt-like structure that links cells. They are calcium dependent.
    • Desmosomes: Patch-like structures that anchor intermediate filaments and provide mechanical strength to tissues subject to stress.
    • Tight Junctions (Zonula Occludens): Seal adjacent cells, forming a barrier to the passage of molecules between them, maintaining cell polarity.
    • Gap Junctions: Composed of connexons, allowing ions and small molecules to pass directly between the cytoplasm of adjacent cells.

    Gap Junctions

    • Gap junctions are specialized inter-cellular communication sites in animal cells.
    • They allow the passage of ions and small molecules between cells.
    • Connexons, comprising the protein connexins, build up gap junctions. These are vital for the synchronized contraction of cardiac muscle cells.

    Tight Junctions (Zonula Occludens)

    • Tight junctions are crucial for maintaining cell polarity and limiting paracellular passage of substances.
    • Key proteins include occludin and claudins.
    • Zonulae occludentes are multiprotein complexes sealing neighbouring cells to maintain their polarity.

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    Description

    Explore the intricate world of cell interactions through this quiz focused on cell-cell and cell-substrate relationships. Test your knowledge on various types of junctions including adherens, gap, tight, and others. Ideal for students studying cellular biology.

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