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Introduction to Prokaryotic Cells - Microbiology

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Termini in questo insieme (30)

  • What are the two prokaryotic domains?
    Bacteria and Archaea are the two prokaryotic domains.
  • How do prokaryotic cells differ from eukaryotic cells?
    Prokaryotes are unicellular, lack a membrane-bound nucleus, and lack membrane-bound organelles.
  • Why are prokaryotes generally small in size?
    Small size allows for a high surface area-to-volume ratio, facilitating efficient nutrient uptake and waste elimination.
  • Define monomorphic and pleomorphic bacteria.
    Monomorphic bacteria have one shape; pleomorphic bacteria can take on different forms, aiding survival and transmission.
  • Name common prokaryotic shapes.
    Common shapes include bacilli (rod-shaped), cocci (spherical), vibrio (comma-shaped), stella (star-shaped), coccobacilli (ovoid), and spirochetes (spiral-shaped).
  • What are common prokaryotic cell arrangements?
    Arrangements include diplococci (pairs), streptococci (chains), staphylococci (clusters), diplobacilli (paired rods), streptobacilli (chains of rods), and palisade (clusters of rods).
  • Describe the process of binary fission.
    DNA is copied, cell grows, chromosomes separate, septum forms at midpoint, and two daughter cells separate.
  • What is the structure and function of the prokaryotic plasma membrane?
    A thin, flexible phospholipid bilayer that acts as a selective barrier controlling substance entry and exit.
  • How do membrane proteins function in prokaryotes?
    They act as transporters, anchors, receptors, and enzymes, and help detect environmental changes.
  • What factors affect membrane fluidity?
    Temperature and fatty acid content; warmer temperatures and unsaturated fatty acids increase fluidity.
  • How do bacterial and archaeal plasma membranes differ?
    Bacteria have linear fatty acids in bilayers; archaea have long-branched fatty acids and can form lipid monolayers.
  • What is the main component of bacterial cell walls?
    Peptidoglycan is the core component of bacterial cell walls.
  • How do Gram-positive and Gram-negative cell walls differ?
    Gram-positive have a thick peptidoglycan layer and no outer membrane; Gram-negative have a thin peptidoglycan layer, outer membrane with lipopolysaccharide.
  • What color do Gram-positive and Gram-negative bacteria stain?
    Gram-positive stain purple; Gram-negative stain red/pink.
  • Why are Gram-negative bacteria often harder to kill with chemicals?
    Their outer membrane acts as a selective barrier protecting against lysozyme, drugs, detergents, and disinfectants.
  • What is acid-fast staining used to detect?
    It detects mycolic acid, a waxy lipid in cell walls of acid-fast bacteria like Mycobacterium and Nocardia.
  • What are the main types of passive transport in prokaryotes?
    Simple diffusion for small noncharged molecules and facilitated diffusion using channel or carrier proteins.
  • Define osmosis and its effects on bacterial cells in different solutions.
    Osmosis is water movement from low to high solute concentration. In hypertonic solutions, cells lose water; hypotonic, cells gain water; isotonic, no net water movement.
  • What are the main types of active transport in prokaryotes?
    Primary active transport uses ATP; secondary active transport uses ion gradients (symport and antiport); phosphotransferase systems modify transported substances.
  • What are flagella and their function in prokaryotes?
    Flagella are protein filaments made of flagellin that rotate like propellers to enable motility.
  • Describe the different flagella arrangements.
    Monotrichous (single), lophotrichous (tuft at one pole), amphitrichous (flagella at both poles), peritrichous (all over surface).
  • What are periplasmic flagella and their role?
    Located between plasma membrane and cell wall, they enable spirochetes to move in a corkscrew motion.
  • What are fimbriae and pili?
    Fimbriae are short, bristle-like structures for adhesion; pili are longer, rigid, fewer, used for adhesion, movement, and gene transfer.
  • What is the glycocalyx and its types?
    A sticky carbohydrate layer; slime layer is loose and unorganized, capsule is well-organized and tightly associated.
  • What is the nucleoid in prokaryotes?
    The nucleoid is the region containing the single, circular chromosome of prokaryotic DNA.
  • Describe prokaryotic ribosomes.
    70S ribosomes made of 50S large and 30S small subunits; synthesize proteins by linking amino acids.
  • What is the function of the prokaryotic cytoskeleton?
    Composed of protein filaments, it provides structure and support to the cell.
  • What are inclusion bodies?
    Distinct collections of substances inside cells used for storage, e.g., carboxysomes and magnetosomes.
  • What are endospores and why are they important?
    Metabolically inactive, highly resistant structures formed by some bacteria to survive harsh conditions.
  • Name medically important spore-forming bacteria.
    Genera Bacillus, Clostridium, and Clostridioides, including species causing anthrax, tetanus, botulism, gas gangrene, and severe diarrhea.