Virus Multiplication Essay

Question 1

What is the attachment phase of virus multiplication

Answer 1

A virus-attachment protein (anti receptor) binds to a cellular receptor molecule. The anti receptors are either glycoproteins or carbohydrate residues. Some viruses use more than one receptor.

Question 2

Why is attachment harder for plant viruses than for animal viruses?

Answer 2

The outer surface of plants are composed of protective layers of waxes and pectin, and each cell is surrounded by a thick wall of cellulose overlying the cytoplasmic membrane

Question 3

What are the 3 mechanisms which viruses can use to enter cells?

Answer 3

Translocation of the entire virus particle across the cytoplasmic membrane of the cell

Endocytosis of the virus into the intracellular vacuoles

Fusion of the virus membrane with the cell membrane

Question 4

Describe the translocation of the entire virus particle across the cytoplasmic membrane of the cell as a mechanism of viral entry

Answer 4

This process is relatively rare among viruses and is poorly understood. It is mediated by proteins in the virus capsid and specific membrane receptors.

Question 5

Describe the endocytosis of the virus into intracellular vacuoles as a mechanism of viral entry

Answer 5

This is probably the most common mechanism of virus entry into cells. It is does not require any specific virus proteins (other than those already utilised for receptor binding) but relies on the normal formation and internalisation of coated pits at the cell membrane.

Question 6

When does uncoating occur?

Answer 6

Occurs after host cell entry during which the virus capsid and occurs simultaneously with or immediately after entry. If a virus has an envelope, the envelope is removed first. Uncoating is usually triggered by the change in pH as the endoscope is acidified

Question 7

What is the ultimate product of uncoating?

Answer 7

Depends on the virus. For example, for picornaviruses, 23 amino acids covalently attached to the 5’ end of the RNA genome

Question 8

Describe the release of non-envelopes viruses

Answer 8

Lysis of the infected cell occurs and virus is released

Question 9

Describe release for enveloped viruses

Answer 9

Enveloped viruses acquire their lipid membrane as the virus buds out of the cell through the cell membrane, or into an intracellular vesicle prior to subsequent release. Vision envelope proteins are picked up during this process as the virus particle is extruded