Cell: The Unit of Life
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Questions and Answers

What is the characteristic of the genetic material in prokaryotes?

  • It is basically naked, not enveloped by a nuclear membrane. (correct)
  • It is divided into multiple chromosomes.
  • It is found in the cytoplasm.
  • It is enveloped by a nuclear membrane.

    • What is the function of plasmid DNA in bacteria?

  • It helps in the destruction of foreign DNA.
  • It confers certain unique phenotypic characters to bacteria. (correct)
  • It regulates the expression of genomic DNA.
  • It helps in the replication of genomic DNA.

    • Which of the following organelles are found in prokaryotic cells?

  • Ribosomes (correct)
  • Mitochondria
  • Golgi apparatus
  • Lysosomes

    • What is the size of typical bacteria?

    <p>1-2 μm</p> Signup and view all the answers

    Which of the following is NOT a characteristic of prokaryotic cells?

    <p>Genomic DNA is enveloped by a nuclear membrane</p> Signup and view all the answers

    What is the function of the cytoplasm in prokaryotic cells?

    <p>It is the fluid matrix filling the cell.</p> Signup and view all the answers

    Which of the following bacteria is an exception to having a cell wall?

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

    What is the significance of plasmid DNA in higher classes?

    <p>It is used to monitor bacterial transformation with foreign DNA.</p> Signup and view all the answers

    What is the approximate length of Mycoplasmas, the smallest cells?

    <p>0.3 µm</p> Signup and view all the answers

    What is a unique feature of prokaryotes?

    <p>Inclusions and infoldings of cell membrane</p> Signup and view all the answers

    What is the typical shape of the bacterium Coccus?

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

    What is the outermost layer of the cell envelope in prokaryotes?

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

    What is the general size range of bacteria?

    <p>0.3 to 5.0 µm</p> Signup and view all the answers

    What is the main function of the cell wall in prokaryotes?

    <p>To maintain the cell's shape and provide structural support</p> Signup and view all the answers

    Which of the following is a characteristic of the plasma membrane in prokaryotes?

    <p>It is selectively permeable in nature</p> Signup and view all the answers

    Which of the following is a characteristic of prokaryotic cells?

    <p>They multiply more rapidly than eukaryotic cells</p> Signup and view all the answers

    What is the name of the smallest isolated single cell?

    <p>Ostrich egg</p> Signup and view all the answers

    What is the term for the process of staining cells to distinguish between Gram-positive and Gram-negative bacteria?

    <p>Gram staining</p> Signup and view all the answers

    Which of the following is an example of a prokaryotic cell?

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

    What is the function of glycocalyx in prokaryotes?

    <p>To protect the cell from the environment</p> Signup and view all the answers

    What is the shape of the bacterium Vibrio?

    <p>Comma-shaped</p> Signup and view all the answers

    What is the term for the infoldings of cell membrane in prokaryotes?

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

    Which of the following is a characteristic of Gram-positive bacteria?

    <p>They take up the Gram stain</p> Signup and view all the answers

    What is the fundamental organization of prokaryotic cells?

    <p>Fundamentally similar to eukaryotic cells</p> Signup and view all the answers

    Study Notes

    Cell Size and Shape

    • Mycoplasmas, the smallest cells, are only 0.3 µm in length.
    • Bacteria can be 3 to 5 µm in length.
    • The largest isolated single cell is the egg of an ostrich.
    • Red blood cells are about 7.0 µm in diameter.
    • Cells vary greatly in shape, including disc-like, polygonal, columnar, cuboid, thread-like, or irregular shapes.

    Prokaryotic Cells

    • Prokaryotic cells include bacteria, blue-green algae, mycoplasma, and PPLO.
    • They are generally smaller and multiply more rapidly than eukaryotic cells.
    • Prokaryotes exhibit a wide variety of shapes and functions.
    • They have a cell wall surrounding the cell membrane, except in mycoplasma.
    • The fluid matrix filling the cell is the cytoplasm.
    • There is no well-defined nucleus in prokaryotes.
    • Genetic material is basically naked, not enveloped by a nuclear membrane.
    • Prokaryotes have plasmids, which are small circular DNA outside the genomic DNA, conferring unique phenotypic characters to bacteria.

    Cell Envelope and Modifications

    • The cell envelope consists of a tightly bound three-layered structure: glycocalyx, cell wall, and plasma membrane.
    • Each layer of the envelope performs distinct functions, but they act together as a single protective unit.
    • Bacteria can be classified into two groups based on the differences in the cell envelopes and the manner in which they respond to the staining procedure developed by Gram.
    • Gram-positive bacteria take up the gram stain, while Gram-negative bacteria do not.

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