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Cell Biology: Prokaryotes vs Eukaryotes
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Cell Biology: Prokaryotes vs Eukaryotes

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Questions and Answers

What is unique about the cell membrane of eukaryotic cells compared to prokaryotic cells?

  • They are double-layered
  • They contain sterols (correct)
  • They contain peptidoglycan
  • They are semi-permeable
  • How do prokaryotic cells, such as bacteria, replicate?

  • By budding
  • By binary fission (correct)
  • By mitosis
  • By meiosis
  • What determines the shape of a bacterium?

  • Its cytoplasmic membrane
  • Its nucleoid
  • Its cell wall (correct)
  • Its cytoplasm
  • How do certain cocci arrange themselves?

    <p>All of the above</p> Signup and view all the answers

    What is the term for bacteria that are variable in shape?

    <p>Pleomorphic</p> Signup and view all the answers

    What is the primary function of the nucleoid in a prokaryotic cell?

    <p>To store genetic material</p> Signup and view all the answers

    Which of the following is a characteristic of prokaryotic DNA?

    <p>It has no introns</p> Signup and view all the answers

    What is the function of pili (fimbriae) in bacteria?

    <p>To adhere to epithelial cells</p> Signup and view all the answers

    What is the purpose of antibiotics that target prokaryotic ribosomes?

    <p>To selectively target prokaryotic ribosomes while sparing eukaryotic ribosomes</p> Signup and view all the answers

    What is the role of capsular polysaccharides in vaccine development?

    <p>They are used as antigens</p> Signup and view all the answers

    What is the approximate concentration of bacteria per milliliter required to see one bacterium per microscopic field using the oil immersion lens?

    <p>100,000 bacteria/mL</p> Signup and view all the answers

    What is the function of teichoic acids in gram-positive bacteria?

    <p>To induce septic shock and mediate attachment to mucosal cells</p> Signup and view all the answers

    What is the location of the peptidoglycan layer in gram-negative bacteria?

    <p>In the periplasmic space</p> Signup and view all the answers

    What are the components of ribosomes in prokaryotic cells?

    <p>rRNA and protein</p> Signup and view all the answers

    What is the region of the cytoplasm that contains DNA in prokaryotic cells?

    <p>Nucleoid region</p> Signup and view all the answers

    Study Notes

    Cell Membrane and Replication

    • Eukaryotic cell membranes contain sterols, whereas prokaryotes (except Mycoplasma) do not.
    • Prokaryotic cells replicate by binary fission, while eukaryotic cells replicate by mitosis.

    Structure of Bacterial Cells

    Shape and Size

    • Bacteria are classified by shape into three basic groups: cocci, bacilli, and spirochetes.
    • Some bacteria are variable in shape and are said to be pleomorphic (many-shaped).
    • The shape of a bacterium is determined by its rigid cell wall.

    Arrangement of Bacteria

    • Certain cocci occur in pairs (diplococci), some in chains (streptococci), and others in grapelike clusters (staphylococci).
    • These arrangements are determined by the orientation and degree of attachment of the bacteria at the time of cell division.

    Gram Stain

    • It takes approximately 100,000 bacteria/mL to see 1 bacterium per microscopic field using the oil immersion (100×) lens.
    • The sensitivity of the Gram stain procedure is low.

    Medically Important Bacteria That Cannot Be Seen in the Gram Stain

    • Meningococcemia is an exception, where high concentrations of Neisseria meningitidis can occur in the blood.

    Special Components of Gram-Positive Cell Wall

    • Teichoic acids are found in Gram-positive bacteria and can induce septic shock.
    • Teichoic acids mediate the attachment of staphylococci to mucosal cells.
    • Gram-negative bacteria do not have teichoic acids.

    Periplasmic Space

    • The periplasmic space is the area between the inner and outer membranes.
    • It contains the peptidoglycan layer and a gel-like solution of proteins.

    Cytoplasmic Membrane

    • The cytoplasmic membrane is a lipid bilayer with selective permeability.
    • It is the site of ATP production.

    Cytoplasm

    • The cytoplasm has two distinct areas: an amorphous matrix and an inner, nucleoid region composed of DNA.
    • The cytoplasm contains ribosomes, nutrient granules, metabolites, and plasmids.

    Structures Inside Cytoplasm

    • Ribosomes consist of rRNA and protein.
    • Protein synthesis occurs at ribosomes and can be inhibited by certain antibiotics.
    • Prokaryotic ribosomes (70s) are different from eukaryotic ribosomes (80s), allowing antibiotics to selectively target prokaryotic ribosomes.

    Nucleoid

    • The nucleoid is the area of the cytoplasm where DNA is located.
    • Bacterial DNA is a single, circular molecule that contains about 2000 genes.
    • Bacterial DNA has no introns, unlike eukaryotic DNA.

    Plasmids

    • Plasmids are extrachromosomal, double-stranded, circular DNA molecules that can replicate independently of the bacterial chromosome.
    • Plasmids carry genes for antibiotic resistance, heavy metal resistance, UV light resistance, pili, and exotoxins.

    Structures Outside the Cell

    • Capsule is a gelatinous layer covering the entire bacterium, composed of polysaccharide.
    • Capsule is a determinant of virulence, limits phagocytosis, and is used in specific organism identification and vaccine production.

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    Description

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