Cell Structure: Cytoskeleton and Microtubules
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Questions and Answers

What role do microfilaments play in intestinal epithelial cells?

  • Serve as storage for cellular nutrients
  • Facilitate cell motility through contraction
  • Support the structure of the plasma membrane
  • Make up the core of microvilli (correct)

    • How do actin-myosin interactions contribute to muscle cells?

  • Enhance the stability of the cell membrane
  • Increase cellular permeability to nutrients
  • Mediate the contraction of muscle cells (correct)
  • Facilitate DNA replication

    • What defines pseudopodia in amoeba?

  • Permanent extensions for nutrient storage
  • Transient structures for locomotion (correct)
  • Rigid appendages for defense
  • Fixed structures for shape maintaining

    • Which of the following is NOT a function of microfilaments?

    <p>Providing structural stability to the nucleus</p> Signup and view all the answers

    In muscle cells, which process is primarily driven by the actin-myosin contractile system?

    <p>Contraction of muscle fibers</p> Signup and view all the answers

    What is the primary function of dynein in the context of microtubules?

    <p>Transporting cargo from the periphery to the cell center</p> Signup and view all the answers

    Which statement regarding kinesin is correct?

    <p>It functions in transporting cargo toward the cell periphery.</p> Signup and view all the answers

    What type of motor protein is responsible for transport toward the plus end of the microtubule?

    <p>Cytosolic kinesin</p> Signup and view all the answers

    In the context of cellular transport, what do motor proteins utilize to carry vesicles?

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

    What characteristic distinguishes the role of kinesin and dynein?

    <p>Kinesin moves toward the + end, while dynein moves toward the - end of microtubules.</p> Signup and view all the answers

    What is the primary function of fibronectin within the extracellular matrix (ECM)?

    <p>Promotes cell attachment to ECM components</p> Signup and view all the answers

    Which collagen type is most abundant in the human body and is crucial for tissue structure?

    <p>Type I</p> Signup and view all the answers

    What structural motif is characteristic of collagen's helical chains?

    <p>Gly-X-Y</p> Signup and view all the answers

    Which collagen type is primarily found in cartilage?

    <p>Type II</p> Signup and view all the answers

    Which syndrome is associated with reduced production of Type I collagen?

    <p>Osteogenesis imperfecta (OI) type I</p> Signup and view all the answers

    What cells primarily produce collagen in the extracellular matrix?

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

    Which type of collagen is associated with the basement membrane?

    <p>Type IV</p> Signup and view all the answers

    What is the primary role of the basement membrane?

    <p>Separates epithelial cells from connective tissue</p> Signup and view all the answers

    What is a primary function of the plant cell wall?

    <p>Protects the plant cell from damage</p> Signup and view all the answers

    Which of the following materials primarily composes plant cell walls?

    <p>Cellulose fibers</p> Signup and view all the answers

    What distinguishes plant cell walls from those of animal cells?

    <p>Composition of cellulose</p> Signup and view all the answers

    Which statement about the cell wall is incorrect?

    <p>It is present in all types of cells.</p> Signup and view all the answers

    Which of these components is found in prokaryotic cell walls, but not in plant cell walls?

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

    What role does the plant cell wall play in regulating water uptake?

    <p>It prevents excessive water uptake.</p> Signup and view all the answers

    Which organisms besides plants are known to possess cell walls?

    <p>Prokaryotes and fungi</p> Signup and view all the answers

    What prevents plant cells from taking in too much water?

    <p>Cell walls</p> Signup and view all the answers

    What is the primary role of the centrosome in the cytoskeleton?

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

    Which of the following structures is a component of the cytoskeleton?

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

    What distinguishes flagella from cilia?

    <p>Cilia drive fluid movement across cell surfaces</p> Signup and view all the answers

    Which of the following correctly describes microfilaments?

    <p>Involved in muscle contraction</p> Signup and view all the answers

    What is a common extracellular component of animal cells?

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

    Which type of junction is primarily responsible for the direct communication between animal cells?

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

    How do plant cells typically connect with each other?

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

    Which statement about intermediate filaments is true?

    <p>They provide mechanical support to cells</p> Signup and view all the answers

    Which motor protein primarily facilitates movement towards the cell periphery along microtubules?

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

    What is the primary function of cilia in eukaryotic cells?

    <p>Enabling locomotion and movement of fluids</p> Signup and view all the answers

    Which statement accurately describes the motion of flagella?

    <p>They have a snakelike undulating motion.</p> Signup and view all the answers

    Which of the following best describes the structure of cilia?

    <p>Specialized arrangements of microtubules</p> Signup and view all the answers

    What is a notable difference between flagella and cilia regarding their number per cell?

    <p>Cilia are typically more numerous than flagella.</p> Signup and view all the answers

    What type of movement pattern do cilia use to propel the cell?

    <p>Back-and-forth motion</p> Signup and view all the answers

    Which end of a microtubule is typically associated with the forward motion of kinesin?

    <p>(+) end</p> Signup and view all the answers

    Which type of cell structure would likely utilize dynein for its function?

    <p>Tracheal cells using cilia</p> Signup and view all the answers

    Study Notes

    Cell Structure and Components

    • The cytoskeleton is a network of filaments throughout the cytoplasm
    • It is composed of three types of filaments:
      • Microfilaments (actin filaments): the thinnest components
      • Intermediate filaments: filaments with middle-range diameters, composed of different protein types (e.g., keratin)
      • Microtubules: tubulin filaments, the thickest of the three components
    • Cytoskeleton functions:
      • Mechanical support for the cell
      • Maintains cell shape
      • Organizes cell structures and activities
      • Allows cell movement
      • Can be assembled and disassembled to change cell shape

    Cytoskeleton: Microtubules

    • Microtubules are hollow rods, the thickest component of the cytoskeleton
    • They are helical polymers made of tubulin monomers
    • Microtubule functions include:
      • Mitotic spindle formation, separating chromosome copies in dividing cells
      • Shaping the cell
      • Guiding organelle movement

    Microtubules: Centrosomes and Centrioles

    • The centrosome is a microtubule-organizing center (MTOC)
    • It consists of a centriole pair
    • Located near the nucleus (cell center)
    • Found only in animal cells
    • Yeast and plant cells do not have centrosomes but may contain similar structures
    • Centrosome structure: has 2 centrioles
    • Centrioles are composed of nine triplets of microtubules (9+0 arrangement)
    • Pericentriolar material surrounds the centrosome
    • Contains y-tubulin that facilitates the nucleation of microtubules

    Microtubules and Motility

    • Microtubules act as "monorails" for the movement of vesicles, organelles, and chromosomes.
    • Motor proteins (cytoplasmic motor proteins) move cargo along microtubules:
      • Dynein: transports material from periphery towards cell center (+ to - end)
      • Kinesin: transports materials from cell center toward periphery (- to + end)

    Cilia and Flagella

    • Cilia and flagella are permanent locomotor appendages of some eukaryotic cells
    • They contain specialized arrangements of microtubules (9+2 arrangement of microtubules)
    • Cilia move in back-and-forth motion
    • Flagella move in a snakelike motion
    • Axoneme: the central strand of cilia and flagella, composed of microtubules
    • Axonemal dynein: responsible for bending movements of cilia and flagella
    • Basal body: a protein structure found at the base of eukaryotic cilia and flagella, consists of nine triplets microtubules (9+0 arrangement)

    Microfilaments (Actin Filaments)

    • Microfilaments are solid rods, composed of two intertwined strands of actin
    • Can be assembled and disassembled to change cell shape
    • Act in muscle contraction
    • Function in cell motility in organisms such as amoebas.
    • Also responsible for microvilli core structures in the intestinal epithelial cells and cytoplasmic streaming processes.

    Intermediate Filaments

    • Intermediate filaments are larger than microfilaments but smaller than microtubules
    • They are more permanent than microfilaments or microtubules
    • Function: provide support to cell shape and fix organelles in place
    • Intermediate filaments help make up desmosomes in epithelial cells
    • Some examples of IF types include keratin, desmin, vimentin, neurofilaments, GFAP and lamins.

    Extracellular Components

    • Most animal cells are covered by the extracellular matrix (ECM)
    • ECM consists of glycoproteins and proteoglycans
    • Glycoproteins include collagen, fibronectin, and laminin
    • Proteoglycans are proteins plus glycosaminoglycans
    • ECM functions overall are to provide support, facilitate adhesion, cell movement, and regulate gene expression.

    Plant Cell Walls

    • Plant cell walls are found outside of the plasma membrane
    • They are an extracellular structure distinct from animal cell walls
    • Plant cell walls consist mostly of cellulose fibers embedded in other polysaccharides and proteins
    • Functions of plant cell walls include: protection for the cell, maintaining its shape, and preventing excessive uptake of water.

    Intercellular Junctions

    • Intercellular junctions are important for cell coordination and communication
    • Plant cells have plasmodesmata: channels that connect neighboring plant cells and allow the exchange of molecules
    • Animal cells have tight junctions, desmosomes, and gap junctions.
      • Tight junctions prevent intercellular leakage of fluid.
      • Desmosomes fasten cells together into strong sheets.
      • Gap junctions provide channels allowing ion and small molecule exchange.

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    Topic 5. Cell Part B PDF

    Description

    This quiz explores the structure and functions of the cytoskeleton, focusing on microtubules and their role within the cell. It covers the different components of the cytoskeleton, such as microfilaments and intermediate filaments, as well as the specific functions that microtubules perform in cellular processes. Test your knowledge on this essential aspect of cell biology!

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