viruses

• viruses are acellular
• acellular - not made of cells
• viruses reproduce inside host cells --> damages host cell and leads to disease
• viruses are non-living --> can not reproduce on their own
• viruses are obligate parasites --> can not survive independently
• Virion

  • complete virus particle
  • dormant form of a virus
  • too small to see with a light microscope
• dormant - not active but can become active
• virions dismantle inside host cells --> allows virus to reproduce
• virions contain:

  1. nucleic acid
  2. protein coat
• nucleic acid

  • single or double stranded DNA/RNA
  • usually codes for 5 - 100 proteins
• protein coat

  • is a capsid made of subunits --> capsomeres
• nucleocapsid - capsid proteins are closely bound to nucleic acid
• Some virions have complex structures:

  1. Enzymes - required to replicate viral nucleic acid or incorporate it into host
  2. Lipid membrane - derived from host cell membrane (has glycoproteins attached)
  3. Matrix proteins - attach capsid to envelope
  4. Glycoproteins - allows virus to attach to host cell
• viruses are smaller than bacteria