Microtubules and Cytoskeleton
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Questions and Answers

Which mitochondrial membrane contains mitochondrial porins and receptors for proteins and polypeptides translocating into the intermembrane space?

  • Mitochondrial matrix membrane
  • Outer mitochondrial membrane (correct)
  • Mitochondrial cristae membrane
  • Inner mitochondrial membrane

    • Where are the proteins contained in the membrane of peroxisomes synthesized?

  • On the rough endoplasmic reticulum (correct)
  • In the peroxisomal lumen
  • On the smooth endoplasmic reticulum
  • In the cytosol

    • What is the function of peroxisomes in the cell?

  • Cell signaling
  • Glycogen synthesis
  • Protein synthesis
  • Fatty acid oxidation and ROS detoxification (correct)

    • Which cell organelle universally contains catalase?

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

    What is the underlying cause of the various metabolic disorders associated with peroxisomes?

    <p>Defects in peroxisomal biogenesis</p> Signup and view all the answers

    What is the role of microtubules in the cell?

    <p>Cytoskeletal polarity</p> Signup and view all the answers

    What is the function of the microtubule-organizing center (MTOC) in the cell?

    <p>Microtubule nucleation and organization</p> Signup and view all the answers

    What is the characteristic of intermediate filaments in the cytoskeleton?

    <p>They have no polarity</p> Signup and view all the answers

    Which cytoskeletal component is associated with kinesin?

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

    What is the function of the terminal web in epithelial cells?

    <p>To anchor the actin filaments of microvilli</p> Signup and view all the answers

    What is the structure of actin microfilaments in the cytoskeleton?

    <p>A double helix of globular actin monomers</p> Signup and view all the answers

    What is the primary function of the G1 DNA-damage checkpoint?

    <p>To allow the repair of damaged DNA before entering the S phase</p> Signup and view all the answers

    What is the function of the Microtubule Organizing Center (MTOC)?

    <p>To organize microtubule polymerization</p> Signup and view all the answers

    What is the main result of the malfunction of the spindle-assembly checkpoint?

    <p>Aneuploid cells with incorrect chromosome number</p> Signup and view all the answers

    What is the function of the unreplicated-DNA checkpoint?

    <p>To ensure the completion of DNA replication</p> Signup and view all the answers

    What is the term for the rapid depolymerization of microtubules?

    <p>Microtubule catastrophe</p> Signup and view all the answers

    What is the function of γ-tubulin rings within the MTOC?

    <p>To nucleate microtubules</p> Signup and view all the answers

    What is the main characteristic of G0 cells?

    <p>Quiescent state with low metabolic activity</p> Signup and view all the answers

    What is the location of the enzymes for β-oxidation of fatty acids?

    <p>Mitochondrial matrix</p> Signup and view all the answers

    What type of nucleic acids are found in mitochondria?

    <p>Both DNA and RNA</p> Signup and view all the answers

    What is the result of a low level of oxidative phosphorylation in mitochondria?

    <p>Vesicular cristae configuration</p> Signup and view all the answers

    What happens to the mitochondrial transmembrane potential when the integrity of the mitochondrion is breached?

    <p>It drops</p> Signup and view all the answers

    What is the function of cytochrome c and SMAC/DIABLO in apoptosis?

    <p>They activate a cascade of proteolytic enzymes</p> Signup and view all the answers

    What is the role of caspases in apoptosis?

    <p>They are the effectors of apoptosis</p> Signup and view all the answers

    What triggers apoptosis?

    <p>Both external and internal stimuli</p> Signup and view all the answers

    What is the role of the BCL-2 family proteins in apoptosis?

    <p>They dictate the predominate interactions between anti-apoptotic and pro-apoptotic proteins</p> Signup and view all the answers

    What happens to the electron-transport chain when the integrity of the mitochondrion is breached?

    <p>It is disrupted</p> Signup and view all the answers

    What is released from the mitochondrial intermembrane space when the integrity of the mitochondrion is breached?

    <p>Proteins from the mitochondrial intermembrane space, including cytochrome c and SMAC/DIABLO</p> Signup and view all the answers

    What is the result of the release of cytochrome c and SMAC/DIABLO from the mitochondrial intermembrane space?

    <p>Caspase activation and subsequent apoptosis</p> Signup and view all the answers

    What is the function of caspases in cellular proteins?

    <p>They cleave more than 100 cellular proteins</p> Signup and view all the answers

    Study Notes

    Microtubules and Cytoskeleton

    • Microtubules are attached to chromosomes at the apical part of an epithelial cell.
    • The minus/plus ends of microtubules and actin microfilaments refer to the direction of their growth and shrinkage.
    • Microtubule catastrophe occurs when a microtubule undergoes rapid depolymerization, leading to its disassembly.
    • Proteins that limit the polymerization of actin microfilaments include actin-binding proteins.
    • Proteins that limit microtubule polymerization in the Microtubule Organizing Center (MTOC) include γ-tubulin rings.
    • The MTOC is a region near the centrioles where microtubules are organized and nucleated.
    • The MTOC works by nucleating and organizing microtubules, which then grow and shrink to form the spindle fibers.
    • The structure of the MTOC consists of γ-tubulin rings and other proteins that nucleate and organize microtubules.
    • Intermediate filaments have no polarity, unlike microtubules and actin microfilaments.
    • Kinesin is associated with microtubules.

    Mitochondria

    • The mitochondrial membrane that contains mitochondrial porins and receptors for proteins and polypeptides translocating into the intermembrane space is the outer mitochondrial membrane.
    • The condensed morphology of mitochondria appears in the presence of high ADP concentrations, while the orthodox configuration occurs at low ADP concentrations.
    • The functions of mitochondria include energy production through ATP synthesis.
    • The underlying cause of various metabolic disorders associated with peroxisomes is a deficiency in peroxisomal biogenesis or function.

    Peroxisomes

    • Peroxisomes are organelles that contain catalase and are involved in various cellular functions, including fatty acid oxidation.
    • The proteins contained in the membrane of peroxisomes are synthesized in the endoplasmic reticulum.
    • The proteins contained in the lumen of peroxisomes are synthesized in the cytosol.
    • The functions of peroxisomes include fatty acid oxidation, amino acid metabolism, and ROS detoxification.
    • Forms of peroxisome biogenesis exist in the cell, including de novo synthesis and inheritance from parent cells.

    Cell Cycle

    • The G1 DNA-damage checkpoint allows the cell to repair DNA damage before entering the S phase.
    • The restriction checkpoint allows the cell to pause and respond to DNA damage before entering the S phase.
    • The functions of the cell cycle include DNA replication, cell growth, and cell division.
    • The principal phases of the cell cycle include the G1, S, G2, and M phases.
    • The G1 phase is the first growth phase, where the cell prepares for DNA replication.
    • The S phase is the DNA synthesis phase, where the cell replicates its DNA.
    • The G2 phase is the second growth phase, where the cell prepares for cell division.
    • The M phase is the mitosis phase, where the cell divides into two daughter cells.
    • Checkpoints exist throughout the cell cycle, including the G1, S, G2, and M phases.
    • The spindle-assembly checkpoint ensures proper spindle formation before the M phase.
    • The chromosome-segregation checkpoint ensures proper chromosome segregation during the M phase.
    • Aneuploid cells are cells that have an abnormal number of chromosomes.
    • Mitotic catastrophe occurs when a cell undergoes aberrant mitosis, leading to cell death.

    Apoptosis

    • The main result of the malfunction of checkpoints is the loss of control over cell growth and division, leading to tumorigenesis.
    • G0 cells are quiescent cells that are not actively growing or dividing.
    • The response to injury is fulfilled by a reserve population of stem cells represented by G0 cells.
    • The loss of contact inhibition is a characteristic of cancer cells.
    • Mitochondria play a critical role in apoptosis, where the release of cytochrome c and other proteins triggers a cascade of proteolytic enzymes.
    • The irreversible release of intermembrane space proteins causes subsequent caspase activation and apoptosis.
    • The BCL-2 family proteins regulate mitochondrial outer membrane permeability and dictate the interactions between anti-apoptotic and pro-apoptotic proteins.

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    Description

    This quiz covers the structure and function of microtubules and cytoskeleton in cells, including their growth, shrinkage, and regulation by proteins. Learn about microtubule catastrophe, actin microfilaments, and more.

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