Viruses

Question 1

What are viruses?

Answer 1

Nucleic acid contained within a protective protein coat. Can infect prokaryotes and eukaryotes.

Question 2

What are the 2 main differences between viruses and bacteria?

Answer 2

1. Antibiotics have no effect 2. Cannot replicate outwith a cellular environment (obligate intracellular parasites; lack critical components for replication)

Question 3

Label the parts that make up a virus:

Answer 3

A - genome

B - capsid

C - envelope

D - envelope glycoprotein

Question 4

Describe the components of a virus

Answer 4

1. Genome - viral nucleic acid
2. Capsid - virus-encoded proteins. Protects genome and facilitates binding/entry of virus into cells
3. Nucleocapsid - genome and capsid collectively
4. Envelope - lipid bilayer derived from cellular membranes during replication in cell. Not all viruses have these.
5. Envelope glycoproteins - Provide viral function, antigens recognised by immune system

Question 5

What shape are viruses?

Answer 5

Icosahedral or helical

Question 6

What are the features of an icosahedral virus?

Answer 6

• 20 faces, faces are equilateral triangle
• Some are enveloped eg. herpes virus
• Some are not enveloped e.g. FMD

Question 7

What are the features of a helical virus?

Answer 7

• Simple
• Small genomes
• Provide protection for the genome without need to encode multiple capsid proteins