Appearance

Living?

Viruses are difficult to class as living organisms as:

• Non cellular
• Only reproduce in a host cell
• Have just one nucleic acid

Reproduction

Requires energy and structures of host cell

Nutrition

Obligate parasites – get energy from host cell

Size

• 50 times smaller than bacteria
• Non-cellular

Role

• Used in genetic engineering to transfer genes
• Vaccine production
• Control of bacterial infections

Disadvantages