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Functional Anatomy of Prokaryotic and Eukaryotic Cells - Microbiology

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  • Key difference between prokaryotic and eukaryotic cells
    Prokaryotic cells lack membrane-enclosed organelles including a nucleus, while eukaryotic cells have a membrane-bound nucleus and other organelles.
  • What is peptidoglycan and where is it found?
    Peptidoglycan is a polymer of NAG and NAM sugars with amino acid chains, found in the cell walls of prokaryotic bacteria but not in eukaryotic cell walls.
  • Basic shapes of bacterial cells
    The three basic bacterial shapes are coccus (spherical), bacillus (rod-shaped), and spiral (twisted).
  • Functions of bacterial glycocalyx
    The glycocalyx (capsule or slime layer) protects pathogens from phagocytosis, enables adherence to surfaces, prevents desiccation, and may provide nutrients.
  • Structure and function of bacterial flagella
    Flagella are long filamentous appendages with a filament, hook, and basal body that rotate to push the cell, enabling motility and taxis.
  • What is bacterial taxis?
    Taxis is movement in response to stimuli: positive taxis is movement toward an attractant, and negative taxis is movement away from a repellent.
  • Role of H antigen in bacteria
    The flagellar protein H antigen is used to distinguish serovars of gram-negative bacteria.
  • What are axial filaments and which bacteria have them?
    Axial filaments (endoflagella) wrap around spiral-shaped spirochetes and enable their unique corkscrew motility.
  • Difference between fimbriae and pili
    Fimbriae help bacteria adhere to surfaces; pili are involved in twitching motility and DNA transfer.
  • Composition of bacterial cell walls
    Bacterial cell walls are made of peptidoglycan, a polymer of NAG and NAM sugars linked by short amino acid chains.
  • Differences between gram-positive and gram-negative cell walls
    Gram-positive walls have many peptidoglycan layers and teichoic acids; gram-negative walls have a thin peptidoglycan layer and an outer membrane with lipopolysaccharides.
  • Function of the outer membrane in gram-negative bacteria
    The outer membrane protects against phagocytosis, penicillin, lysozyme, and chemicals; it contains porins for molecule passage and lipopolysaccharides as endotoxins.
  • What is the role of lipopolysaccharide (LPS) in gram-negative bacteria?
    LPS consists of O polysaccharides that act as antigens and lipid A, which is an endotoxin causing toxic effects.
  • How does the Gram stain differentiate bacteria?
    Crystal violet–iodine complex binds peptidoglycan; decolorizer removes outer membrane in gram-negative bacteria washing out the dye, differentiating gram-positive (purple) and gram-negative (pink).
  • What are atypical bacterial cell walls?
    Some bacteria like Mycoplasma lack cell walls; Archaea have pseudomurein instead of peptidoglycan; acid-fast bacteria have mycolic acid layers.
  • Effect of lysozyme on bacterial cell walls
    Lysozyme destroys gram-positive cell walls producing protoplasts; gram-negative walls are partially destroyed producing spheroplasts.
  • Role of penicillin in bacterial cell wall synthesis
    Penicillin interferes with the synthesis of peptidoglycan, weakening the bacterial cell wall and causing cell lysis.
  • Structure and function of the plasma membrane in bacteria
    The plasma membrane is a lipid bilayer with proteins, selectively permeable, containing enzymes for metabolism and energy production.
  • Types of transport across bacterial plasma membranes
    Transport includes passive diffusion, facilitated diffusion, osmosis, active transport (energy-dependent), and group translocation (chemical modification during transport).
  • What is the nucleoid in bacteria?
    The nucleoid is the region containing the bacterial chromosome DNA; bacteria may also have plasmids, which are extrachromosomal circular DNA molecules.
  • Characteristics of bacterial ribosomes
    Bacterial ribosomes are 70S, composed of rRNA and protein, and are the site of protein synthesis.
  • What are bacterial endospores?
    Endospores are dormant, resistant structures formed by some bacteria to survive adverse environmental conditions.
  • Differences between eukaryotic and prokaryotic flagella and cilia
    Eukaryotic flagella are few and long; cilia are numerous and short. Both have a 9+2 microtubule arrangement and are used for motility; cilia also move substances along cell surfaces.
  • Composition of eukaryotic cell walls
    Algal cell walls contain cellulose; fungal walls contain chitin; yeast walls have glucan and mannan; animal cells lack walls but have a glycocalyx.
  • Unique features of the eukaryotic plasma membrane
    Eukaryotic plasma membranes have phospholipid bilayers with proteins, carbohydrates, and sterols; they perform passive and active transport plus endocytosis.
  • Functions of the rough and smooth endoplasmic reticulum
    Rough ER has ribosomes for protein synthesis and transport; smooth ER synthesizes lipids.
  • Role of mitochondria and chloroplasts in eukaryotic cells
    Mitochondria produce ATP and contain 70S ribosomes and DNA; chloroplasts perform photosynthesis and also have 70S ribosomes and DNA.
  • What is the endosymbiotic theory?
    The theory states eukaryotic cells evolved from symbiotic prokaryotes living inside other prokaryotic cells.