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Microbiology: Prokaryotic Cell Structure and Function

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  • Name two prokaryotic domains.
    The two prokaryotic domains are Bacteria and Archaea.
  • Do prokaryotic organisms contain membrane-bound organelles? Are prokaryotes multicellular or unicellular?
    Prokaryotes do not contain membrane-bound organelles and are typically unicellular.
  • What does it mean if a bacterium is pleomorphic? What advantage does it give the microbe?
    A pleomorphic bacterium can vary in shape and size, allowing it to adapt to different environments.
  • How do most prokaryotes obtain nutrients?
    Most prokaryotes obtain nutrients through absorption from their environment.
  • Describe common prokaryote shapes and arrangements.
    Common shapes include cocci (spherical), bacilli (rod-shaped), and spirilla (spiral). Arrangements vary like chains, clusters, or pairs.
  • What reproduction process is used by most prokaryotes? Is it sexual or asexual?
    Most prokaryotes reproduce by binary fission, an asexual process.
  • Describe the basic structure and main function of a prokaryotic plasma membrane.
    The plasma membrane is a phospholipid bilayer that controls selective transport of substances in and out of the cell.
  • Where is the cell wall located relative to the plasma membrane in prokaryotes?
    The cell wall is located outside the plasma membrane, providing structural support and protection.
  • What is the core component of bacterial cell walls?
    The core component of bacterial cell walls is peptidoglycan.
  • What is the core component of archaea cell walls?
    Archaea cell walls lack peptidoglycan and often contain pseudopeptidoglycan or other unique polymers.
  • What glycolipid enriches the outer membrane of Gram-negative bacteria?
    The outer membrane contains lipopolysaccharide (LPS), a glycolipid.
  • Which part of lipopolysaccharide acts as an endotoxin?
    The lipid A portion of LPS acts as an endotoxin.
  • Where in the body are enteric bacteria commonly found?
    Enteric bacteria are commonly found in the intestinal tract.
  • Why are Gram-negative bacteria less susceptible to penicillin than Gram-positive bacteria?
    Gram-negative bacteria have an outer membrane that blocks penicillin from reaching the peptidoglycan layer.
  • Name two genera of acid-fast bacteria.
    Two well-known acid-fast genera are Mycobacterium and Nocardia.
  • Are acid-fast organisms considered Gram-positive or Gram-negative?
    Acid-fast organisms are considered Gram-positive despite a weak Gram stain reaction.
  • Which bacterial genus lacks cell walls?
    The genus Mycoplasma lacks cell walls.
  • What is the difference between L-forms and Mycoplasma?
    L-forms are bacteria that lose their cell walls temporarily, while Mycoplasma naturally lack cell walls.
  • What is the difference between active and passive transport?
    Active transport requires energy to move substances against a gradient; passive transport does not require energy and moves substances down a gradient.
  • What is diffusion? Is it active or passive?
    Diffusion is the passive movement of molecules from high to low concentration.
  • What is the difference between simple diffusion and facilitated diffusion?
    Simple diffusion moves molecules directly through the membrane; facilitated diffusion uses protein channels or carriers.
  • What is osmosis? Is it active or passive?
    Osmosis is the passive diffusion of water across a selectively permeable membrane.
  • What is the function of flagella in prokaryotes?
    Flagella provide motility, allowing bacteria to move.
  • Define chemotaxis and phototaxis.
    Chemotaxis is movement toward or away from chemicals; phototaxis is movement in response to light.
  • What is the function of fimbriae and pili?
    Fimbriae help with attachment to surfaces; pili assist in DNA transfer between cells.
  • How do bacterial capsules increase pathogenicity?
    Capsules protect bacteria from phagocytosis and help adhere to host tissues.
  • What is the main molecule contained in the nucleoid region of bacteria?
    The nucleoid contains the bacterial chromosomal DNA.
  • What is the function of ribosomes in prokaryotes?
    Ribosomes synthesize proteins by translating mRNA.
  • How do prokaryotic ribosomes differ from eukaryotic ribosomes?
    Prokaryotic ribosomes are 70S (50S + 30S), while eukaryotic ribosomes are 80S (60S + 40S).
  • What supports the endosymbiotic theory regarding chloroplasts and mitochondria?
    Chloroplasts and mitochondria have 70S ribosomes similar to prokaryotes, supporting their bacterial origin.
  • What is the function of the prokaryotic cytoskeleton?
    The cytoskeleton helps maintain cell shape and assists in cell division.
  • What are inclusion bodies and their function?
    Inclusion bodies store nutrients or energy reserves inside the cell.
  • How do endospores differ from vegetative cells?
    Endospores are dormant, resistant forms that survive harsh conditions; vegetative cells are metabolically active.
  • Name three genera that produce medically relevant endospores.
    The genera Bacillus, Clostridium, and Clostridioides produce medically important endospores.