Virology Flashcards
Give the basic structural components of a virus
- Nucleic acid
- Protein coat
- Protein spikes
- Lipid envelope (only in some viruses)
Describe the genome of a virus
- very small
- either RNA or DNA, never both
Describe the protein coat of a virus
- Encases the nucleic acid
- Made of repeating subunits
- A simple geometric structure
Describe the source of lipid coat some viruses have
It is derived from the host cell
Give 2 examples of possible symmetry shown by viruses
Icosahedral
Helical
Describe the features of an icosahedral symmetrical virus
- 20 sided spheroid
- 3 subunit types (apex, edge, flat)
Describe the features of an helically symmetrical virus
- 1 single repeating unit
- 1 repeating unit, so only 1 gene required
List the phases of a viral life-cycle
- Attachment
- Entry
- Uncoating
- Nucleic acid & protein synthesis
- Assembly
- Release
Describe how a virus attaches to a host cell
Protein spike acts as a ligand and binds to a cell surface receptor
Why do viral infections often stay localised?
As during the viruses protein spike is a specific ligand to a certain cell surface receptor type
Only some cells express that receptor. Virus can’t spread to cells without it
Describe how a virus enters a host cell once attached
Viral and cell membranes fuse
OR
Endocytosis - The virus binding to the receptor triggers endocytosis
Describe viral uncoating
The virus sheds its protein coat once inside the cell
Describe how viral protein synthesis occurs in a host cell
- Viral nucleic acid is used as instructions to produce viral proteins
- Host ribosomes used
Describe viral assembly inside host cells
- Nucleic acid and proteins are packaged together
- Form crystals of assembling viruses (visible in some cells as inclusions)
Give the 2 types if viral release from a host cell
Budding and lysis
Describe viral release by budding
The virus encases itself in an lipid envelope (cell membrane) to leave the cell
What kinds of virus often release via budding
Viruses that have a lipid envelope
Describe viral release by lysis
- Viruses accumulate in the host cell
- Eventually the viruses lyse the cell and are released
List possible targets for antiviral grugs
- Viral enzymes (nucleic acid synthesis)
- Viral enzymes (viral protein synthesis)
- Attachment
- Entry
- Uncoating
- Release
Name a class of antivirals that affect the immune system
Immune adjuvants
Describe the purpose of immune adjuvants
To affect to immune system to better allow it to deal with the viral infection
What is rational drug design?
- Molecular analysis of viral targets to design a molecule that may inhibit its function
- Instead of blindly testing
(doesn’t work for bacteria as they are to complex)
Where might antiviral resistance seen?
After long periods of treatment
Especially if immunocompromised
Describe how viral infections are damaging to a host organism
- Cell death by lysis or hijacking of cell machinery
- Cell death by immune cells
