Viruses overview

Question 1

What is a virus?

Answer 1

A tiny infectious particle, consisting of a nucleic acid core surrounded by a protein coat called a capsid

Question 2

Size of a Virus?

Answer 2

250A (yellow fever) - 2500A (Smallpox)

Question 3

Properties of a virus

Answer 3

• Require living organisms/host to reproduce
• They lie on the threshold between life and non-life
• They are nor cellular, do not respire, have no metabolism, do not breakdown carbon compounds, do not fix carbon dioxide, do not die

Question 4

What do they generally do?

Answer 4

• Viruses by their nature interrupt normal cell cycle and may cause:
  ○ Benign or malignant growths
  ○ Asymptomatic
  ○ Viral Virulence:
  § Narrow host range: can infect only one species
  § Broad host range: can infect different species of mammals

Question 5

Viral Structure

Answer 5

○ 3 morphological classifications:
§ Helical
§ Icosahedral: based on a geometric icosahedron of 2o equilateral triangular faces
Combined or complex structures

○ The core consists of either DNA or RNA (not both)
○ Surrounded by protein capsid of varying geometrical configuration
○ Some viruses have a lipoprotein envelope in addition, which is derived from the membrane of the host cell

Question 6

Bacteriophage

Answer 6

A type of virus that infects bacteria