Viruses

The structure of viruses

  • Viruses are non-living because they:

    • are non-cellular

    • cannot reproduce independently (they require a host)

    • do not grow or respond to stimuli

    • do not carry out protein synthesis (they use the protein-building machinery in host cells)

    • They have no metabolic activity

  • All viruses are parasitic

  • They are much smaller than prokaryotic and eukaryotic cells

  • Structurally they have:

    • Genetic material: either DNA or RNA, and can be single or double-stranded

    • A capsid: a protein coat surrounding genetic material and containing attachment proteins

    • Attachment proteins: these bind to receptors on host cells during invasion

Diagram of a virus showing a capsid, protein molecules, and DNA or RNA genetic code, with labelled parts in a circular and helical structure.