1.1.7

Viruses

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Viruses

Viruses are acellular and non-living. Virus particles include genetic material, a capsid and attachment proteins.

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Structure

  • Viruses are made up of nucleic acids. Viruses can be either DNA or RNA viruses, depending on the nucleic acids they are made up from.
  • The nucleic acids form the core of the virus are surrounded by a protein called a capsid.
  • Viruses are smaller than bacteria.
  • Some viruses are surrounded by a phospholipid envelope exterior to the protein capsid.
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Living cells

  • Viruses are NOT considered living because:
    • They have no nucleus, plasma membrane, cytoplasm or ribosomes.
    • They are not made of cells.
    • They cannot reproduce independently.
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Function

  • To replicate, viruses have to invade and hijack the reproductive mechanism of a living cell. These cells are then termed host cells.
  • Viruses have attachment glycoproteins that bind to complementary receptors on host cells.
  • They then inject DNA or RNA into the host cell.
  • The host cell divides as normal and the virus is replicated.

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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