Virus structure Flashcards
1
Q
Describe the nature of viruses
A
- Differ from bacterial and mammalian cells
- Only one type of nucleic acid (either DNA or RNA)- may be single or double-stranded
- Virus synthesise protein using host cell ribosomes
- Can only grow in living cells
- Viruses multiply by independent synthesis of constituent parts (self-assembly)- which form new virus
2
Q
Describe the size of viruses
A
- Much smaller than bacteria
- Most only visible through an electron microscope
- Major structural contraint
- Genetic information in nucleic acid limited
- Small viruses, e.g. polio, only have 3-4 genes
3
Q
Describe the protein ‘building blocks’ that form viruses
A
- Capsomeres
- Assemble to form a capsid, virus shell
- Protects nucleic acid from physical, chemical or enzymatic damage
- Can either be arranged in helical or icosahedral shape
4
Q
What makes up the nucleoocaspid?
A
- Capsid + genome
5
Q
What is a lipid envelope and what is the purpose of it?
A
- Viruses budding from host cell membrane will acquire a lipid envelope
- Lipid envelope has lipid bilayer os host cell membrane where host’s proteins were removed and replaced with viral glycoproteins
- Mediate attachment and penetration of virus into host cell
- Serve as potential targets for immune system
6
Q
Why is a lipid envelope useful?
A
- Very thermodynamically efficient way of packing asymmetric capsomeres
- Form approx. spherical space for nucleic acid to use symmetry in which capsid is based on icosahedron
7
Q
What is the benefit of self-assembly?
A
- Faulty capsomeres cannot assemble
- Allows fault-free assembly
8
Q
How are viruses classified?
A
- Genome complexity
- Symmetry of the capsid
- Presence of envelope
- Nomenclature
- Can be discoverer/disease/morphology
9
Q
How does a virus spread?
A
- Oral transmission
- Direct inoculation or sexual transmission
- Inhalation (droplet)
- Skin contact
10
Q
How are viruses controlled by vaccination?
A
- First vaccines were live (against smallpox and rabies)
- Production of attenuated yellow fever virus made in chick embryos which provided complete protection
- Poliomyelitis- 1st vaccine produced using viruses propagated in cell culture (live eukaryotic cells)
- Followed by MMR vaccine (all attenuated)
- Some recently developed with DNA technology (Hep B)
11
Q
Describe polio
A
- Harmless to babies but attacked adults when hygiene improved around the world
- Affects autonomous nervous system, causes respiratory issues
- Gut virus
- Iron lung invented to aid breathing
12
Q
Describe mumps
A
- Affects carotid gland
- Negative strand RNA virus
13
Q
Describe rubella
A
- Dangerous in pregnant women
- Congenital rubella in new borns
