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Prokaryotic Cell Structure and Function - Microbiology

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Termini in questo insieme (32)

  • Main differences between prokaryotic and eukaryotic cells

    Prokaryotic cells lack a nucleus and membrane-bound organelles, have smaller size, and simpler structure compared to eukaryotic cells which have a nucleus and complex organelles.

  • Common bacterial shapes and arrangements

    Bacterial shapes include coccus (spherical), bacillus (rod), vibrio (comma-shaped), spirilli (spiral). Arrangements depend on division planes and include chains, clusters, pairs.

  • Meaning of monomorphic, pleomorphic, coccobacillary

    Monomorphic: single shape; Pleomorphic: variable shapes; Coccobacillary: short rods resembling cocci.

  • Three types of spiral bacteria and differences

    Vibrio (curved rods), spirilli (rigid helices), spirochetes (flexible helices). Differ in rigidity and motility mechanisms.

  • Effect of plane of division on bacterial arrangement

    Division in one plane forms chains; two planes form tetrads; multiple planes form clusters or packets.

  • Cell arrangements in cocci and bacilli

    Cocci: singles, diplococci, chains, clusters; Bacilli: singles, pairs, palisades. MreB protein maintains rod shape in bacilli.

  • Structures found in all bacterial cells

    Cell membrane, cytoplasm, ribosomes, nucleoid (DNA), and cell wall.

  • Structures external to bacterial cell wall

    Glycocalyx (capsules and slime layers), flagella, pili, fimbriae, axial filaments.

  • What is glycocalyx?

    A gelatinous polysaccharide or polypeptide layer outside the cell wall that protects bacteria and aids in attachment.

  • Capsules vs slime layers

    Capsules are well-organized, firmly attached, and protect against phagocytosis; slime layers are loose, unorganized, and aid in attachment.

  • Function and structure of bacterial flagellum

    Flagellum enables motility; composed of filament, hook, and basal body which work together for rotation and movement.

  • Flagellar run and tumble

    Run: flagella rotate counterclockwise for smooth swimming; Tumble: clockwise rotation causes random reorientation.

  • Pili and fimbriae functions

    Fimbriae aid in attachment to surfaces; pili facilitate DNA transfer during conjugation.

  • Axial filaments (endoflagella)

    Located in spirochetes, wrapped around the cell between outer sheath and cell wall, enabling corkscrew motility.

  • Main component of bacterial cell wall

    Peptidoglycan, a polymer of sugars and amino acids forming a mesh-like layer.

  • Peptidoglycan structure

    Alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) sugars crosslinked by short peptides.

  • Components unique to gram-positive cell walls

    Thick peptidoglycan layer with teichoic acids (wall teichoic and lipoteichoic acids) that provide rigidity and charge.

  • Differences between gram-positive and gram-negative cell walls

    Gram-positive: thick peptidoglycan, teichoic acids; Gram-negative: thin peptidoglycan, outer membrane with lipopolysaccharides.

  • Atypical bacterial cell walls and examples

    Cell walls lacking typical peptidoglycan, e.g., Mycobacterium with mycolic acid, and Archaea with pseudopeptidoglycan.

  • Mycolic acid and its bacterial genera

    Long-chain fatty acids in cell walls of Mycobacterium and Nocardia, providing waxy, hydrophobic properties.

  • Bacteria lacking cell walls and membrane composition

    Mycoplasma lack cell walls; their membranes contain sterols for stability.

  • Factors damaging bacterial cell walls

    Lysozyme, penicillin, detergents, and physical damage can disrupt peptidoglycan integrity.

  • Protoplasts, spheroplasts, and L-forms

    Protoplasts: G+ cells without cell wall; Spheroplasts: G- cells with partial wall; L-forms: wall-deficient variants.

  • Main components and functions of bacterial inner membrane

    Phospholipid bilayer with proteins; functions include selective permeability, energy production, and transport.

  • Hopanoids in bacterial membranes

    Sterol-like molecules that stabilize bacterial membranes, similar to cholesterol in eukaryotes.

  • Bacterial outer membrane composition and function

    Outer leaflet: lipopolysaccharides (LPS); inner leaflet: phospholipids; functions include protection and selective permeability.

  • Three major components of LPS and endotoxin

    Lipid A (endotoxin), core polysaccharide, and O antigen; Lipid A causes toxic effects in hosts.

  • Porins in gram-negative bacteria

    Proteins forming channels in the outer membrane allowing passage of small molecules.

  • Differences in periplasmic space between G+ and G- bacteria

    G- have a large periplasmic space containing cell wall; G+ have a smaller periplasmic space.

  • Functions of MreB protein

    Maintains rod shape by organizing cell wall synthesis in bacilli.

  • Type of ribosomes in bacteria and archaea

    Both have 70S ribosomes composed of 50S and 30S subunits.

  • Endospores: function and formation

    Highly resistant dormant structures formed by some bacteria to survive harsh conditions; formed by sporulation.