Virology 1 Flashcards
What are viruses?
Filterable, crystallisable and lack a cellular structure (acellular)
Why are viruses considered a non-living organism?
Do not metabolise - no ATP producing system, no ribosomes or means of protein synthesis
Do not reproduce
Do not grow
Do not develop
Do not respond to environment
Do not divide by binary fission
Unable to exist independently out width host cell
What can viruses infect?
Animals, plants, invertebrates, fungi and bacteria
Describe the features of a viral structure
Virion - mature viral particle out with host cell consisting of either DNA or RNA, not both
Capsid - protective protein coat
Nucleocapsid - viral capsid and nucleic acid together
Protomers - capsomers - identical protein subunits that make up capsid
Spikes or Peplomers - attachment proteins from capsid
What are the 2 basic types of virions?
Naked - consists of outer protein capsid + nucleic acid eg. Bacteriophages, adenoviruses
Enveloped - additional covering outside capsid
- consists of double layer lipid similar to host cell membrane of eukaryotic cell
- matrix protein inside envelope
What size are viral genomes?
Small - hepatitis B only 4 genes, herpes 100s and E.coli 4,000
What 4 types of nucleic acid types are found in viruses?
Single stranded DNA
Double stranded DNA
Single stranded RNA
double stranded RNA
Features of capsids
Protein coat composed of repeating protein subunits
May be enveloped or non-enveloped
May have helical or icosahedral symmetry
May have a complex structure
Protects viral genome from host
Name some viral structures (5)
Helical Icosahedral Enveloped Poxvirus Bacteriophages
Describe a helical virus capsid
Hollow protein cylinders
Genetic material wound inside
Many plant viruses have helical symmetry
No naked helical animal viruses
Describe a icosahedral virus capsid
Regular polyhedron
20 equilateral triangular faces and 12 vertices
Composed of hexameter and pentamers
Describe an enveloped virus
Outer membrane structure
Lipids and carbohydrates from host plasma membrane
Proteins in the envelope coded for by virus
Enveloped virus may be helical or icosahedral
How are viruses classified?
Family - viridae Classification based on - nucleic acid - Host - Structure (symmetry) - enveloped - size
What ways are there for identifying viruses?
Microscopy - electron - immunofluorescence Viral culture Serology (identifying antibody) Molecular techniques - PCR (polymerase chain reaction)
What are so,eg uses of bacteriophages?
Studies on viral replication
Molecular biology - transduction - transfer of genes from one bacterium to another; transfer of virulence factors
Typing of bacteria strains can be differentiated by sensitivity to sets of phage
Phage therapy to treat infections eg MRSA, P. aeruginosa infected burns
Treatment of ready to eat food products to remove pathogens
