Viruses ✅ Flashcards
What are the most common cause of human infection?
Viruses
How big are viruses?
20-300nm
Can viruses be visualised with a light microscope?
No
What are viruses dependent on?
Host cells
Why are viruses dependent on cells?
They are unable to synthesise their own enegy or proteins, and so are dependent on the host cells to replicate it
What is a single virus particle known as?
Virion
What can happen within hours of a virion infecting a cell?
It can replicate to produce hundrens of virions
What does the rapid replication of a virion inside a cell allow?
Viruses to spread rapidly from cell to cell
What do viruses consist of structurally?
Core of nucleic acid surrounded by the capsid
What is the capsid?
A protective coating
What is the capsid made up of?
Repeating subunits (capsomeres)
What do the capsomeres of a virus determine?V
Viral geometric symmetry
What are the potential forms of viral geometric symmetry?
- Helical
- Icosahedral
What does the capsid mediate?
The attachment of the virus to specific host cell receptors
What is the implication of the capsid mediating attachment to specific host cell receptors?
It defines the species and organ specificity of the virus
What might the capsid of a virus induce in the host?
Host immune response
What does the nucleic acid of a virus contain?
The genome
Delete
Delete
What is the capsid and the genome of a virus collectively known as?
The nucleocapsid
What is the capsid of a virus sometimes covered by?
A lipoprotein envelope
What does the lipoprotein envelope surrounding some viruses consist of?
- Lipid envelope
- Glycoprotein spikes
What is the lipid envelope of some viruses derived from?
The host cell membrane
What is the purpose of glycoprotein spikes on the lipoprotein envelope of some viruses?
It aids attachment to the host cell
How do viruses with a glycoprotein envelope compare to those without?
Viurses WITH the envelope are LESS STABLE
Give an example of an enveloped virus?
RSV
In what way are enveloped viruses less stable than those without?
- Dry out rapidly in the environment
- Easily inactivated by detergent and alcohol
Give 2 viruses without an envelope
- Rotavirus
- Norwalk virus
What is the classification of viruses based on?
- Viral nucleic acid (DNA or RNA)
- Capsid
- Presence of envelope
What features of the capsid of a virus can classification be based on?
- Size
- Symmetry
What are the potenital consequences of viral infection of a host cell?
- Cell death
- Fusion of host cells
- Malignant transforation
- Chronic carriage
- Latent infection
How can viruses cause cell death?
Inhibition of host cell protein synthesis while allowing ongoing viral protein synthesis
What can be used to visualise cell death caused by viruses?
Light microscopy
How can cell death caused by viruses be visualised by light microscopy?
As the cytopathic effect (CPE) in cell cultures
What is formed by fusion of host cells caused by viruses?
Multinucleated giant cells
Where can multinucleated giant cells caused by viruses be visualised?
In cell cultures
Give an example of a virus that causes fusion of host cells?
RSV
How can viruses lead to malignant transformation?
By causing unrestrained growth, prolonged survival, and morphological changes of the cell
Give an example of a virus that can cause malignant transformation
HPV
When can chronic carriage of a virus occur?
When there is viral replication without killing of the host cell
What might disease result from in chronic virus carriage?
- Direct damage from virus itself
- Host inflammatory response against viral antigens
When does latent viral infection occur?
When the virus remains within the cell but doesn’t replicate
What group of viruses cause latent infection?
All herpesviruses
What happens following primary infection with varicella zoster virus?
It enters a latent phase
What does VZV cause when reactivated?
Shingles
