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General Biology: Microbial Life and Protists

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  • Two broadest domains of cellular life based on nucleus presence

    Prokaryotic (no nucleus) and Eukaryotic (has a nucleus).

  • Domains that are prokaryotic

    Bacteria and Archaea.

  • Location and shape of bacterial DNA

    Circular DNA found in the nucleoid region (no membrane).

  • Ribosome sizes in prokaryotes vs. eukaryotes

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

  • Cell division methods in prokaryotes and eukaryotes

    Prokaryotes divide by binary fission; eukaryotes divide by mitosis (or meiosis for sex cells).

  • Key differences between prokaryotic and eukaryotic cells

    Size (smaller vs. larger), nucleus (absent vs. present), organelles (absent vs. present), DNA shape (circular vs. linear), ribosome size (70S vs. 80S), cell division (binary fission vs. mitosis).

  • Archaea cell wall composition difference from bacteria

    Archaea cell walls lack peptidoglycan, unlike most bacteria.

  • Definition of extremophiles

    Organisms that thrive in extreme environments, such as very hot or salty conditions.

  • Purpose of bacterial cell wall

    Prevents cell bursting by resisting internal osmotic pressure.

  • What is peptidoglycan?

    A rigid mesh-like polysaccharide and protein complex forming the main structure of bacterial cell walls.

  • Difference between Gram-positive and Gram-negative bacteria cell walls

    Gram-positive have a thick peptidoglycan layer and no outer membrane; Gram-negative have a thin peptidoglycan layer plus an outer membrane.

  • Functions of the glycocalyx

    Promotes cell attachment and protects from dehydration; important in biofilm formation.

  • Difference between capsule and slime layer

    Capsule is organized, dense, and tightly attached; slime layer is unorganized and loosely attached.

  • Primary functions of pili

    Cell motility (twitching/gliding) and DNA transfer via conjugation.

  • Difference between fimbriae and pili

    Fimbriae are shorter, more numerous, and function in adhesion; pili are longer and involved in motility and DNA transfer.

  • What are endospores?

    Dormant, highly resistant bacterial cells formed to survive harsh conditions.

  • Is binary fission a form of reproduction in eukaryotes?

    No, binary fission is a prokaryotic asexual reproduction method only.

  • Three mechanisms of horizontal gene transfer in bacteria

    Transformation, Transduction, and Conjugation.

  • What is transformation in bacteria?

    Uptake of free environmental DNA by a competent cell.

  • What is conjugation in bacteria?

    Direct DNA transfer between two bacterial cells via a pilus requiring donor and recipient.

  • What is the F plasmid?

    A conjugative plasmid in E. coli that directs its own transfer during conjugation.

  • Nutritional factors used to classify microbes

    Energy source, electron source, and carbon source.

  • Difference between phototrophs and chemotrophs

    Phototrophs get energy from sunlight; chemotrophs get energy from chemical compounds.

  • Difference between autotrophs and heterotrophs

    Autotrophs fix CO₂ to make carbon molecules; heterotrophs consume organic molecules for carbon.

  • Five oxygen requirement classes of microbes

    Obligate aerobes, facultative anaerobes, microaerophiles, obligate anaerobes, aerotolerant anaerobes.

  • What is a biofilm?

    A community of cells encased in a sticky polysaccharide matrix adhered to a surface.

  • Definition of nitrogen fixation

    Conversion of atmospheric N₂ into usable forms like NH₄ or NO₂ by prokaryotes.

  • What is toxigenicity?

    The ability of a pathogen to produce toxins that damage host cells.

  • What is a protist?

    A diverse, paraphyletic group of eukaryotic organisms that are not plants, animals, or fungi.

  • What is primary endosymbiosis?

    A eukaryotic cell engulfing a prokaryotic cell, leading to organelles like mitochondria and chloroplasts.

  • What is alternation of generations?

    A life cycle alternating between multicellular diploid (sporophyte) and haploid (gametophyte) forms.