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Prokaryotic Cell Structure Quiz
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Prokaryotic Cell Structure Quiz

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Questions and Answers

What is the main function of capsules in bacteria?

  • To provide energy storage
  • To assist in photosynthesis
  • To facilitate respiration
  • To confer protection against phagocytosis (correct)

    • Which structure is NOT typically found in prokaryotic cells?

  • Plasma membrane
  • Ribosomes
  • Cell wall
  • Mitochondria (correct)

    • What distinguishes the slime layer from capsules?

  • Capsules can only be found in Gram-negative bacteria
  • Slime layer is diffuse and unorganized, easily removed (correct)
  • Capsules are composed of proteins only
  • Slime layer is well organized and difficult to remove

    • What is the role of the S-layer in bacterial cells?

    <p>To maintain shape and rigidity of the cell</p> Signup and view all the answers

    How does the glycocalyx aid bacteria?

    <p>By enabling attachment to solid surfaces</p> Signup and view all the answers

    Where is the nucleoid located in a prokaryotic cell?

    <p>In the cytoplasm</p> Signup and view all the answers

    Which characteristic is typical of the structure of capsules?

    <p>Composed mainly of carbohydrates</p> Signup and view all the answers

    What is a distinguishing feature of Archaea compared to Bacteria?

    <p>Ability to live in extreme environments</p> Signup and view all the answers

    What is the main function of the cell wall in bacteria?

    <p>Helps maintain cell shape and protects from osmotic lysis</p> Signup and view all the answers

    Which characteristic is true for Gram-positive bacteria?

    <p>They have a thick peptidoglycan layer</p> Signup and view all the answers

    What primarily composes the structure of peptidoglycan?

    <p>N-acetylglucosamine and N-acetylmuramic acid</p> Signup and view all the answers

    Which statement accurately describes D-amino acids in bacterial cell walls?

    <p>Their presence protects bacteria from proteolytic enzymes</p> Signup and view all the answers

    How do antibiotics typically affect pathogenic bacteria?

    <p>By inhibiting cell wall synthesis</p> Signup and view all the answers

    What distinguishes Gram-negative bacteria from Gram-positive bacteria?

    <p>Presence of two distinct layers in their cell walls</p> Signup and view all the answers

    Which of the following amino acids is commonly found in bacterial cell wall peptides?

    <p>D-alanine</p> Signup and view all the answers

    What is the significance of the Gram stain in microbiology?

    <p>It helps in differentiating bacteria based on their cell wall structure</p> Signup and view all the answers

    What forms the helical backbone in the peptidoglycan structure?

    <p>Alternating NAG and NAM residues</p> Signup and view all the answers

    Which is a characteristic feature of Gram-positive cell walls?

    <p>Presence of teichoic acids</p> Signup and view all the answers

    What important roles does lipopolysaccharides (LPS) play in Gram-negative bacteria?

    <p>Contribute to negative surface charge and protect against toxins</p> Signup and view all the answers

    What is located in the periplasmic space of Gram-negative bacteria?

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

    What is the size range of the thin peptidoglycan layer in Gram-negative bacteria?

    <p>2 to 7 nm</p> Signup and view all the answers

    Which statement is true about Braun's lipoprotein?

    <p>It is covalently linked to peptidoglycan in the outer membrane</p> Signup and view all the answers

    What describes the fluid mosaic model of membrane structure?

    <p>Proteins float within a flexible lipid bilayer</p> Signup and view all the answers

    What is the role of teichoic acids in Gram-positive bacteria?

    <p>Contribute to the cell wall's negative charge</p> Signup and view all the answers

    What is the primary function of pili in most bacteria?

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

    What distinguishes sex pili from other types of pili?

    <p>Their diameters are typically larger.</p> Signup and view all the answers

    Which type of flagellation refers to bacteria having a single flagellum at each end?

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

    How are bacterial flagella primarily useful in identifying bacterial species?

    <p>Through their patterns of distribution</p> Signup and view all the answers

    What role can flagella play apart from motility?

    <p>They can aid in attachment to surfaces.</p> Signup and view all the answers

    What is the typical diameter of bacterial pili?

    <p>3 to 10 nm</p> Signup and view all the answers

    In what form of bacterial reproduction are sex pili specifically involved?

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

    Which type of bacterial flagellation consists of flagella distributed evenly over the entire cell surface?

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

    What is the primary function of the flagellar motor in bacteria?

    <p>To generate rotation for movement</p> Signup and view all the answers

    Which structure is most complex in a flagellum?

    <p>Basal body</p> Signup and view all the answers

    In Gram-positive bacteria, how many rings does the basal body typically have?

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

    What type of movement is characterized by a bacterium moving smoothly from one spot to another?

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

    What is the primary type of flagella present in swarming bacteria?

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

    What is the term for the movement of bacteria in response to chemical gradients?

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

    How do periplasmic flagella function in Spirochete bacteria?

    <p>They rotate within the periplasmic space</p> Signup and view all the answers

    What distinguishes twitching motility from gliding motility?

    <p>Twitching is jerky; gliding is smooth</p> Signup and view all the answers

    Study Notes

    Prokaryotic Cell Structure

    • Prokaryotes are categorized into two groups: Bacteria and Archaea.
    • Escherichia coli is a common example of bacteria, measuring 1.1 to 1.5 µm in width and 2.0 to 6.0 µm in length.

    Prokaryotic Cell Structures

    • Key components of a prokaryotic cell include cell envelope, cell wall, periplasmic space, plasma membrane, nucleoid, plasmids, ribosomes, and storage inclusions.

    Cell Envelope

    • The outer layer of the cell wall is known as the cell envelope, which can take various forms such as capsules, slime layers, glycocalyx, or S-layers.
    • Capsules: Well-organized polysaccharide layers that aid in evading host defenses and protect against desiccation.
    • Slime Layer: Unorganized, easily removable polysaccharide layer that aids in motility.
    • Glycocalyx: Network of polysaccharides aiding in attachment to tissues.
    • S-Layers: Regularly structured protein or glycoprotein layers that assist in cell shape maintenance and defense.

    Cell Wall

    • The cell wall, located outside the plasma membrane, is crucial for maintaining cell shape and protecting against osmotic lysis and toxic substances.
    • Bacteria are categorized as Gram-positive (purple stain) or Gram-negative (pink stain) based on Gram staining.
    • Gram-positive cell walls: Composed of a thick layer (20-80 nm) of peptidoglycan with teichoic acids, providing rigidity and a negative charge.
    • Gram-negative cell walls: Feature a thin peptidoglycan layer (2-7 nm) surrounded by an outer membrane consisting of lipopolysaccharides (LPS).

    Peptidoglycan Structure

    • Peptidoglycan consists of alternating sugars N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
    • Short peptides from NAM extend outward, and D-amino acids in these peptides provide resistance against host enzymes.

    Periplasmic Space

    • Found between the cell wall and plasma membrane; it is larger in Gram-negative bacteria (30-70 nm) than in Gram-positive bacteria.
    • Contains periplasm, contributing to cellular function and maintaining integrity.

    Plasma Membrane

    • Follows the fluid mosaic model, representing a lipid bilayer where proteins are embedded, allowing for flexibility and functionality.

    External Structures

    • External structures like pili, fimbriae, and flagella extend beyond the cell envelope, aiding in attachment, motility, and gene transfer.
    • Pili and fimbriae: Thin appendages primarily for attachment; type IV pili participate in DNA uptake during transformation.
    • Flagella: Long, threadlike structures enabling motility; vary in arrangement (monotrichous, amphitrichous, lophotrichous, peritrichous).

    Flagellar Movement

    • Flagella rotate to propel the bacterium in a swimming motion; smooth running and tumbling movement alternate to navigate.
    • Spirochete bacteria employ periplasmic flagella for movement, rotating within the cell.

    Swarming and Chemotaxis

    • Swarming is a group behavior among motile bacteria, often observed in colonies on solid surfaces.
    • Chemotaxis allows bacteria to move toward attractants or away from repellents, modifying movement patterns based on environmental gradients.

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    Related Documents

    BT-Sem 1 topic -1.2.pdf

    Description

    Test your knowledge on prokaryotic cell structure, including the characteristics and components of bacteria and archaea. Learn about the cell envelope, cell wall, and various structures such as capsules and slime layers. This quiz covers essential information for understanding the basic units of life.

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