Bacterial Structures and Motility
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Questions and Answers

Which statement accurately describes the movement of spirochetes due to their axial filaments?

  • They move exclusively in a straight line.
  • They can only move in a backward motion.
  • They exhibit a spiral or corkscrew-like movement. (correct)
  • They move by undulating like cilia.
  • What type of bacteria possess flagella distributed over their entire surface?

  • Amphitrichous bacteria
  • Peritrichous bacteria (correct)
  • Lophotrichous bacteria
  • Monotrichous bacteria
  • Which type of motility involves the use of pili?

  • Ciliary movement
  • Amoeboid movement
  • Gliding motility (correct)
  • Flagellar propulsion
  • What is the primary function of fimbriae in bacteria?

    <p>Attachment to surfaces</p> Signup and view all the answers

    Bacteria that lack flagella are classified as what type?

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

    What is a key function of the bacterial capsule?

    <p>Protecting bacteria from being phagocytized</p> Signup and view all the answers

    What distinguishes a slime layer from a capsule?

    <p>A slime layer is loose and water-soluble.</p> Signup and view all the answers

    What structural component primarily makes up bacterial flagella?

    <p>Protein called flagellin</p> Signup and view all the answers

    How does energy generation affect bacterial motility through flagella?

    <p>Flagellar rotation relies on the continuous generation of energy.</p> Signup and view all the answers

    Which type of movement do spirochetes exhibit due to their unique flagellar structure?

    <p>Spiral or helical movement</p> Signup and view all the answers

    What is the term for the movement of bacteria toward or away from a chemical stimulus?

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

    What pattern of movement do bacteria exhibit when they approach an attractant?

    <p>Long runs and few tumbles</p> Signup and view all the answers

    What does a flagellum NOT contain?

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

    What is the primary feature of the glycocalyx that distinguishes it from other cell structures?

    <p>It is a viscous, gelatinous material.</p> Signup and view all the answers

    Which type of cell division is characteristic of prokaryotic cells?

    <p>Binary fission</p> Signup and view all the answers

    What is the main function of a slime layer in bacteria?

    <p>To facilitate motility and adherence to surfaces.</p> Signup and view all the answers

    Which of the following best describes the structure of flagella in prokaryotic cells?

    <p>They consist of a hook, a filament, and a basal body.</p> Signup and view all the answers

    What are bacilli commonly characterized by?

    <p>They can be short, long, thick, or thin.</p> Signup and view all the answers

    Which type of bacteria are described as being monomorphic?

    <p>Those that maintain a single shape.</p> Signup and view all the answers

    How do spirilla bacteria primarily move?

    <p>Using flagella in a corkscrew motion.</p> Signup and view all the answers

    What is a common occurrence in the arrangement of diplo- and streptococci?

    <p>They occur in pairs or chains.</p> Signup and view all the answers

    Study Notes

    Glycocalyx

    • A viscous, gummy material composed of sugars and proteins
    • Produced by the cell membrane and secreted outside the cell.
    • Classified as a slime layer or a capsule

    Slime Layer

    • Unorganized
    • Only loosely attached to the cell wall
    • Enables bacteria to glide or slide along solid surfaces

    Capsule

    • Organized and firmly attached to the cell wall
    • Composed of polysaccharides, with possible combinations with lipids and proteins
    • Protects bacteria from being engulfed by white blood cells (phagocytosis).

    Flagella

    • Threadlike protein appendages that enable bacteria to move.
    • The presence of flagella indicates a motile bacterium
    • Flagellated bacteria are about 10 to 20 nanometers (nm) thick
    • Composed of protein fibers called flagellin, twisted together like a rope.
    • Prokaryotic flagella do not have microtubules and are not membrane-bound.

    Axial Filament

    • Two flagella-like fibrils
    • Wrap around the organism
    • Enable spirochetes to move in a spiral or helical fashion

    Flagellum Structure

    • Arises from a basal body in the cell membrane
    • Projects outward through the cell wall and capsule.
    • A semirigid, helical structure that rotates from the basal body
    • Rotation is clockwise or counterclockwise
    • Flagellar rotation relies on continuous energy production by the cell

    Bacterial Movement

    • Bacteria can alter the speed and direction of flagellar rotation
    • The movement of bacteria towards or away from a stimulus is called taxis

    Chemotaxis

    • Movement toward or away from chemical stimuli
    • Oxygen, ribose, and galactose are examples of chemical stimuli

    Phototaxis

    • Movement toward or away from light stimuli
    • Motile bacteria contain receptors to detect stimuli

    Pili and Fimbriae

    • Observed on Gram-negative bacteria
    • Polymerized protein molecules called pilin, arranged in a helix
    • Extend from the cytoplasm through the plasma membrane, cell wall, and capsule.

    Fimbriae (Adhesin)

    • Located at the bacterial cell poles or evenly distributed on the surface
    • Important for bacterial attachment to surfaces

    Pili

    • Usually longer than fimbriae
    • Typically only one or two per cell
    • Involved in bacterial motility and DNA transfer
    • Enable gliding motility.

    Bacterial Shape

    • Monomorphic: maintains a single shape
    • Pleomorphic: can have multiple shapes

    Prokaryotic Cell Structure

    • All bacteria are prokaryotes
    • Significantly smaller than eukaryotic cells
    • Reproduction occurs through binary fission
    • The cytoplasm contains a chromosome, ribosomes, and other particles
    • Surrounded by a cell wall, sometimes with a capsule or slime layer

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    Description

    This quiz explores the various structures of bacteria, including glycocalyx, slime layers, capsules, flagella, and axial filaments. Understand the functions and characteristics of these structures and their role in bacterial motility and protection. Test your knowledge on prokaryotic cell structures!

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