Viruses: Definition and Key Characteristics

 Identify key characteristics that clearly distinguish viruses from all other organisms:

• Viruses are obligatory intracellular parasites
• Viruses are not cells, but rather submicroscopic particles
• Virus particles are produced from assembly of pre-formed components
• Viruses do not reproduce by division, but replicate in the living cells of the host
• Viruses do not possess biochemical or genetic means to generate the energy
• Viruses lack the ability to make their own protein synthesis machinery (ribosome)