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Microbiology: Prokaryotic and Eukaryotic Cell Structure and Function

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Termini in questo insieme (23)

  • Cell Theory

    1. All living organisms are composed of one or more cells.
    2. The cell is the basic unit of structure and organization in organisms.
    3. Cells arise from pre-existing cells.

  • Major Classes of Organic Molecules in Cells

    Cells are made from nucleic acids, proteins, carbohydrates, and lipids.

  • Three Domains of Life

    Bacteria and Archaea (prokaryotes) have circular chromosomes; Eukarya have linear chromosomes. Operons are present in Bacteria and Archaea but absent in Eukarya.

  • Prokaryotic Cell Shapes

    Coccus (round), Bacillus (rod), Vibrio (curved rod), Coccobacillus (short rod), Spirillum (spiral), Spirochete (long helical spiral).

  • Common Prokaryotic Cell Arrangements

    Single cocci, diplococci (pairs), tetrads (groups of four), streptococci (chains), staphylococci (clusters), single bacillus, streptobacilli (chains of rods).

  • Glycocalyx

    A viscous, gelatinous layer outside the cell wall made of polysaccharides and/or polypeptides; includes slime layers and capsules.

  • Capsule Function

    Protects bacteria from phagocytosis, enhances virulence, blocks immune recognition, and helps form biofilms.

  • Slime Layer Characteristics

    Unorganized, easily removed polysaccharide/glycoprotein layer that protects cells from antibiotics and desiccation and aids adhesion to surfaces.

  • S-layer

    Protein or glycoprotein surface layer that self-assembles, providing protection against environmental stresses and host immune defenses.

  • Flagella Structure

    Composed of filament (flagellin protein), hook, and basal body; enables bacterial motility by rotation.

  • Flagella Function

    Allows bacteria to move toward or away from stimuli (taxis) by rotating to run or tumble.

  • Archaella

    Archaeal motility structures made of archaellins; rotate like flagella but use ATP for energy.

  • Axial Filaments (Endoflagella)

    Found in spirochetes; anchored at one end and cause corkscrew movement by rotation.

  • Fimbriae

    Hairlike appendages that allow attachment to surfaces and are involved in biofilm formation.

  • Pili

    Appendages involved in DNA transfer (conjugation pili) and motility (gliding and twitching).

  • Prokaryotic Cell Wall Composition

    Made of peptidoglycan, a polymer of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) linked by polypeptides.

  • Gram-Positive Cell Wall

    Thick peptidoglycan layer with teichoic acids and lipoteichoic acids; stains purple in Gram stain.

  • Gram-Negative Cell Wall

    Thin peptidoglycan layer between inner membrane and outer membrane containing lipopolysaccharide (LPS); stains pink in Gram stain.

  • Gram Staining Mechanism

    Crystal violet-iodine complexes retained in thick peptidoglycan of Gram-positive cells; washed out in Gram-negative cells due to outer membrane dissolution.

  • Acid-Fast Cell Walls

    Similar to Gram-positive but with mycolic acid waxy coating; resists Gram stain and retains carbolfuchsin dye.

  • Mycoplasmas

    Prokaryotes lacking a cell wall; membrane stabilized by sterols; pleomorphic shapes.

  • Archaeal Cell Walls

    May lack walls or have walls made of pseudomurein, which lacks NAM and D-amino acids.

  • Prokaryotic Cell Membrane

    Phospholipid bilayer with peripheral, integral, and transmembrane proteins; contains glycoproteins and glycolipids.