Cell Biology Quiz: Gap Junctions
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Questions and Answers

What is the primary function of tight junctions?

  • To provide structural support to tissues
  • To create a seal to prevent leaks between cells (correct)
  • To allow for the passage of large molecules between cells
  • To facilitate communication between cells

    • Gap junctions are present only in plant cells.

    False (B)

    What are the two main families of channel-forming proteins involved in gap junctions?

    Connexins and Innexins

    The largest functional pore size for gap-junctional channels is about ______ nm.

    <p>1.5</p> Signup and view all the answers

    Match the following structures with their functions:

    <p>Tight junctions = Prevent leakage between cells Gap junctions = Facilitate communication between cells Plasmodesmata = Allow passage of molecules between plant cells Basal lamina = Provides structural support and acts as a filter</p> Signup and view all the answers

    Which of the following can pass through gap junctions?

    <p>Inorganic ions (C)</p> Signup and view all the answers

    Both connexins and innexins are found only in vertebrates.

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

    What is the significance of gap junctions in pacemaker cells of the heart?

    <p>Gap junctions allow the synchronized electrical activity of pacemaker cells, ensuring coordinated heartbeats.</p> Signup and view all the answers

    Which of the following molecules can pass through gap junctions?

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

    Gap junctions are formed by the alignment of connexons from two adjacent cells.

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

    A connexon is made up of six transmembrane _____ subunits.

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

    Match the following terms with their descriptions:

    <p>Connexon = A hemichannel formed by six connexin subunits Hemichannel = A connexon that does not align with another connexon, opening to the extracellular space Gap junction = A continuous aqueous channel formed by the alignment of two connexons</p> Signup and view all the answers

    What is the primary reason why gap junctions in different tissues exhibit varied properties?

    <p>The presence of different connexins forming the channels (C)</p> Signup and view all the answers

    Unpaired gap junction channels, also known as hemichannels, are typically open, allowing continuous flow of molecules.

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

    What is the primary consequence of mutations in connexin-26?

    <p>Hearing loss due to cell death in the organ of Corti due to disruption of ions in its sensory epithelium</p> Signup and view all the answers

    The neurotransmitter ______ plays a crucial role in regulating gap junction permeability between neurons in the retina, enabling the eye to adapt to varying light intensities.

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

    Explain how dopamine contributes to the regulation of gap junction permeability in the retina.

    <p>Dopamine reduces gap junction permeability between retinal neurons in response to increased light intensity, facilitating a shift from rod receptors to cone receptors for improved vision in bright light.</p> Signup and view all the answers

    Match the following terms with their respective descriptions:

    <p>Connexin = A protein that forms gap junctions Hemichannel = An unpaired gap junction channel Lucifer Yellow = A dye used to study gap junction permeability Organ of Corti = The sensory epithelium of the inner ear Dopamine = A neurotransmitter that regulates gap junction permeability</p> Signup and view all the answers

    Gap junctions are always open once they are formed.

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

    Basal lamina is absent beneath epithelia.

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

    Why do certain bacteria secrete enzymes that can digest components of the basal lamina?

    <p>To gain access to nutrients or to invade tissues.</p> Signup and view all the answers

    What is the main cell type found in connective tissue that secretes extracellular matrix components?

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

    The basal lamina provides guidance to cells regarding the location of ______ and the direction of axonal extension.

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

    What is the neurotransmitter released by the neuron at the neuromuscular junction?

    <p>Acetylcholine (ACh)</p> Signup and view all the answers

    What happens to dopamine levels in the retina when you wake up in the morning and turn on the light?

    <p>Dopamine release is increased. (B)</p> Signup and view all the answers

    What role does dopamine play regarding gap junctions?

    <p>It closes gap junctions (C)</p> Signup and view all the answers

    The basal lamina is a type of extracellular matrix found only in muscle tissues.

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

    What is the primary function of the basal lamina?

    <p>To provide structural support and anchorage for cells.</p> Signup and view all the answers

    The extracellular matrix is primarily composed of __________ and polysaccharides.

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

    Why does the retina utilize the closure of gap junctions in bright light?

    <p>To prevent overwhelming stimuli (D)</p> Signup and view all the answers

    The basement membrane is another name for the basal lamina.

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

    Match the following tissues with their corresponding extracellular matrix:

    <p>Bone = Bulky connective tissue Tendon = Collagen-rich matrix Skin = Dermal layer matrix Muscle = Surrounded by basal lamina</p> Signup and view all the answers

    The basal lamina is typically __________ to __________ nm thick.

    <p>40</p> Signup and view all the answers

    What is the role of the laminin γ-1 chain?

    <p>It is crucial for embryonic development in mice. (D)</p> Signup and view all the answers

    Type IV collagen only exists in one isoform.

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

    What type of protein interacts with the binding sites on laminin?

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

    Laminin has binding sites for __________, which help it connect to other extracellular matrix components.

    <p>perlecan and dystroglycan</p> Signup and view all the answers

    Which of the following is NOT a function of laminin?

    <p>Providing tensile strength to the basal lamina (A)</p> Signup and view all the answers

    Match the following proteins to their functions:

    <p>Laminin = Interacts with integrins and ECM components Type IV Collagen = Provides tensile strength to the basal lamina Integrins = Membrane proteins that connect cells to ECM Nidogen = Fibrous protein that contributes to ECM structure</p> Signup and view all the answers

    Both laminin and type IV collagen contribute to the basal lamina's structure.

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

    What is the structural composition of type IV collagen?

    <p>Three separately synthesized long protein chains</p> Signup and view all the answers

    Study Notes

    Lecture 6: Passageways from Cell to Cell and Basal Lamina

    • Tight junctions prevent extracellular molecules from leaking between cells. They form a seal between cells.
    • Gap junctions create direct passageways between the cytoplasm of adjacent cells. These are different in animal tissues (gap junctions) and plants (plasmodesmata).
    • Gap junctions and plasmodesmata allow for the exchange of small molecules, but not large macromolecules.
    • Tight junctions are protein complexes, creating a seal between cells to prevent leakage.
    • Gap junctions are protein channels that allow small molecules to pass between cells.
    • Connexins and innexins are channel-forming proteins in gap junctions.
    • Gap junctions are crucial for electrical coupling in tissues like the heart.
    • Gap junction channels have a pore size of roughly 1.5 nm, letting small molecules, but not large ones, pass.
    • Ions can pass easily, complex carbs and proteins cannot.
    • Mutations in connexin-26 are associated with congenital deafness.
    • Gap junctions are gated channels (they close on occasion) in contrast to ion channels that stay open all the time.
    • Dopamine regulates gap junction communication.
    • Basal lamina is not made entirely of cells.
    • Basal lamina is a network of macromolecules.
    • Basal lamina is found in tissues like bone, tendon, and skin.
    • Basal lamina is essential for supporting and organizing tissues.
    • Basal lamina is a filter in kidney glomeruli.
    • Basal lamina is important for cell polarity, metabolism, and differentiation.
    • Defects in basal lamina proteins can cause problems in tissue organization.
    • Basal lamina helps hold tissue components in place.
    • Laminin is a major component of the basal lamina, a network of protein fibers and polysaccharides.
    • Type IV collagen is another main component of the basal lamina, providing strength and structural support.

    Laminin

    • Laminin is the primary organizer of the basal lamina structure, crucial in development.
    • Laminin is composed of three polypeptide chains held together by disulfide bonds.
    • Laminin isoforms exist with different properties, and are crucial in cell organization and structure.
    • Laminin is essential for early development.

    Type IV Collagen

    • Type IV collagen is a major contributor to the tensile strength of the basal lamina.
    • It consists of three protein chains, assembling into felt-like networks.
    • Type IV collagen and laminin are structured in a way that enables them to interact.

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    Lecture 6 2025 (PDF): Passageways from Cell to Cell and Basal Lamina

    Description

    Test your knowledge on the structure and function of gap junctions in cells. Explore their primary roles, the proteins involved, and their significance in various tissues. This quiz will enhance your understanding of cellular communication and junctional dynamics.

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