1.1.6

Prokaryotic Cells

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Prokaryotic Cells

Prokaryotic cells have some features that are also found in eukaryotic cells. Prokaryotic cells may also contain plasmids, a capsule and one or more flagella.

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Prokaryotes vs eukaryotes

  • Features common to these types of cells are:
    • A plasma membrane.
    • Cytoplasm.
    • DNA.
    • Ribosomes (ribosomes are 70S in prokaryotes).
  • So, the main difference in terms of organelles is that prokaryotes do NOT have any membrane-bound organelles (e.g. nucleus, mitochondria, Golgi apparatus etc.).
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Features of prokaryotic cells

  • Key features of prokaryotic cells are:
    • 70S ribosomes.
    • Unicellular.
    • No membrane-bound organelles.
    • Typicall 1-5μm in diameter.
    • Peptidoglycan (PPG) cell wall.
    • No nucleus.
    • Circular DNA.
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DNA in prokaryotes

  • Prokaryotic DNA is found as a circular molecule in the cytoplasm.
  • Some prokaryotes have smaller loops of DNA called plasmids that are not part of the main circular DNA molecule.
  • Bacteria can exchange plasmids with other bacteria, sometimes receiving beneficial new genes that the recipient can add to their chromosomal DNA.
    • Antibiotic resistance is one trait that often spreads through a bacterial colony through plasmid exchange.
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Capsule

  • The capsule enables prokaryotic cells to attach to surfaces in its environment.
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Flagella, pili and fimbriae

  • Some prokaryotes have flagella, pili, or fimbriae:
    • Flagella are tail-like and used for locomotion.
      • Some prokaryotes have none and others have more than one.
    • Pili are used to exchange genetic material during a type of reproduction called conjugation.
    • Fimbriae are used by bacteria to attach to a host cell.

Jump to other topics

1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

8Transport in Mammals

9Gas Exchange

10Infectious Diseases

11Immunity

12Energy & Respiration (A2 Only)

13Photosynthesis (A2 Only)

14Homeostasis (A2 Only)

15Control & Coordination (A2 Only)

16Inherited Change (A2 Only)

17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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