Week 3 - Microbiology Viral Structure Flashcards
Viruses - 2 types
Prokaryotic - bacteriophage
Eukaryotic - ex. animal viruses
Prokaryotic vs Eukaryotic
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What is a bacteriophage?
Bacteriophages sit on surface of cells and inject material into them
oblicate intracellular parasites
Need a host to survive
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What are characteristics of virusis
Obligate Intracellular Parasites (they need a host)
Viral particle is DNA or RNA in a protein coat (with or with out membrane)
Outercoat protects the genetic material and facilitates adhesion/infection
Contains NO enzymes, organelles or other biosynthetic machinery
Nucleic acids code for proteins needed for viral replication
Why are there not many anti-virals
Viruses have no ribosomes…
So if a drug targets inhibition of protein synthesis of virus it will also inhibit protein synthesis of the host
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Enveloped viruses
Acquire membrane from host
Naked capsid viruses
Consist of the nucleic material with a coat or capsid
Viral structure is made of?
Envelope
Nucleocapsid/Capsid
Capsomer
Polyhedral/Helical
Envelope
Gets from host
Nucleocapsid/capsid
Protects DNA or RNA of virus
Plyhedral/helical
Different Capsid structures
Capsomere
Subunit of capsid structure
Viroids
Very small single stranded circles of RNA (300 - 400 nucleotides)
Cause disease in PLANTS
Replication strategy unknown - prob through host RNA polymerase
HDV (Hep D virus) is similar to viroid
HDV
Hep D virus - is similar to Viroid
Prions
‘Slow virus diseases’
Resistant to:
heat inactivation (autoclaving)
radiation damage
nucleases (DNAases and RNAases) - they contain NO nucleic acid
What can prions be inactivated by?
Detergents
Urea
Phenol
What are Prions resistant to?
Autoclaving
Radiation
Nucleases
Examples of Prion diseases
Spongiform Encephylopathies
Scrapie
Kuru
Creutzfeldt-Jacob Disease
‘Mad Cow’
Scrapie
Prion disease in sheep
Kuru
Human prion disease in cannibals in Papua New Guinea
Mad Cow Disease
BSE - Prion disease
Causes vCJD in humans
Cruzs jacob disease
Human prion disease
The source is unknown but it is thought to be a variant of BSE (mad cow)
PrPc
Is a noromal human protein.. Function unknown
When this protein folds differently (PrPsc).. It has different conformational shape that causes the proteins around it to also fold into the similar shape which leads to the disease…PRION diseases
Proteases can degrade PrPc but NOT PrPsc after it folds differently…
How is prion protein PrPsc folded differently
PrPc has 3 alpha helices and one beta sheet…
PrPsc has 2 alpha helicies and 4 beta sheets
Prion protein catalyzes formation of itself!
What tells alot about virus?
DNA or RNA
Capped or naked
Polyhedral or helical
