Viral Structure Flashcards
How are viruses similar to living organisms?
proteins
glycoproteins
nucleic acids
How are viruses dissimilar to living organisms?
no polysaccharides
lipids are only found in enveloped viruses
viruses don’t have ribosomes (arenavirus exception)
Describe characteristic of DNA viruses.
Single or double stranded
linear or circular
open or closed ends
continuous or nicked
Describe characteristics of RNA viruses.
single (+ / - sense) or double stranded
linear
may be segmented
What is positive sense?
5’ to 3’
What is negative sense?
3’ to 5’
List the component of the basic virion.
Nucleic acid
Capsid - protein coat that encloses nucleic acid
-made of capsomers
Tegument - proteinaceous material between envelope and capsid
Envelope - not in all viruses
Name the two basic capsid symmetries of the viral forms.
Icosahedral Symmetry - (adenovirus)
Helical Symmetry - (ebola)
Why is the enveloped virus more susceptible?
susceptible to chemical agents that can dissolve lipids
What is the benefit of the viral envelope?
facilitates attachment
How is a naked virus mediate attachment?
Viral attachment protein (VAP)
How is a naked virus released from the host cell? enveloped?
Naked - lysis
Enveloped - budding
What is an example of a complex virus?
poxvirus
What type of genome is in a helical (enveloped) virus?
ssRNA
What type of genome is in a helical (naked) virus?
dsDNA, ssDNA, ssRNA
What type of genome is in an icosahedral (enveloped) virus?
dsDNA, dsRNA, ssRNA
What type of genome is in an icosahedral (naked) virus?
dsDNA, ssDNA, dsRNA, ssRNA
Which capsid type only contains ssRNA?
helical enveloped
Which capsid type has all four genomes?
icosahedral naked
Which capsid type has both DNA genomes but only ssRNA?
helical naked
Which capsid type has both RNA genomes but only dsDNA?
icosahedral enveloped
What factors affect tropism?
- Can the virus get into the host cell?
1a. - can use more than one receptor to gain entry into one type of host cell
1b. -can use the same receptor to gain entry into many different cells - If it enters cell, is the appropriate machinery available. Host cell must be in a stage for replication.
- After replication can the infectious virion get out and spread infection?