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Microbiology: Prokaryotic and Eukaryotic Cell Structures and Functions

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  • Three basic shapes of microbes

    Cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped).

  • What is meant by arrangement in cocci?

    Arrangement refers to how cocci cells group together, such as chains, clusters, or pairs.

  • Unique features of prokaryotic cells

    Single circular chromosome, cell wall chemicals like peptidoglycan, and reproduction by binary fission.

  • Unique features of eukaryotic cells

    Multiple linear chromosomes, cell wall chemicals (varies), mitosis, membrane-bound organelles, and a nucleus with histones.

  • Common structures in both prokaryotes and eukaryotes

    Cell membrane, cytoplasm, ribosomes, and DNA (though organized differently).

  • Cell membrane structure and function

    Proteins and lipid bilayer form a semi-permeable membrane for transport; described by the fluid mosaic model.

  • Peptidoglycan composition

    Polymer of alternating sugars NAM and NAG linked by peptide chains.

  • Gram-positive cell wall features

    Thick peptidoglycan layer with teichoic acids.

  • Gram-negative cell wall features

    Thin peptidoglycan layer, outer membrane with LPS (lipopolysaccharide), including O-polysaccharide and Lipid A endotoxin, plus periplasm and porins.

  • Acid-fast cell wall characteristic

    Contains mycolic acid, a waxy lipid that resists staining.

  • Capsule function and structure

    Gelatinous outer layer that protects against phagocytosis and aids in attachment.

  • Prokaryotic flagella structure

    Composed of filament, hook, and basal body made of flagellin protein.

  • Flagella patterns on cells

    Mono-, peri-, amphi-, and lopho- flagellation describe number and location of flagella.

  • Types of bacterial movement and taxis

    Movement includes runs (CCW rotation) and tumbles (CW rotation); taxis is movement toward attractants or away from repellents via receptors.

  • Axial filament (endoflagella)

    Flagella located within the periplasmic space of spirochetes, enabling movement in viscous environments.

  • Pili and fimbriae functions

    Attachment to surfaces, virulence factors; sex pili enable DNA transfer during conjugation.

  • Nucleoid in prokaryotes

    Region containing the single circular DNA chromosome, not membrane-bound.

  • Ribosome differences: 70S vs 80S

    Prokaryotes have 70S ribosomes; eukaryotes have 80S ribosomes.

  • Role of mitochondria

    Present in eukaryotes; site of energy production via aerobic respiration.

  • Inclusion bodies in prokaryotes

    Storage granules for nutrients or substances; help maintain osmotic balance.

  • Endospore characteristics

    Highly resistant survival structures formed by Bacillus and Clostridium; not for reproduction.

  • Sporulation and germination

    Sporulation forms a spore from a vegetative cell; germination forms a vegetative cell from a spore.

  • Why are endospores survival structures only?

    They enable survival under harsh conditions but do not function in reproduction or multiplication.

  • Atypical prokaryotes: archaea and mycoplasma

    Archaea have unique cell wall chemicals; mycoplasma lack a cell wall entirely.

  • Periplasmic space in Gram-negative bacteria

    Gel-like space between outer membrane and plasma membrane containing enzymes and transport proteins.