viral structure Flashcards
what is a fundamental way in which viruses differ from bacteria?
bacteria can encode their own protein synthesis machinery where as virus cannot (virus needs host cell)
is a virus a living cell?
no
what type of “parasite” is a virus?
obligate intracellular
-compltely dependent on living host cell for reproduction
what components make up a virion (infectious viral particle)
capsid
envelope
glycoproteins
what is a capsid and what is its function?
-viral protein coat that surrounds the nucleic acid genome
-allows *attachment to host cell
what is a viral envelope?
lipid membrane derived from host cell membrane as virus bud out of host cell
-steal from the host cell
(lipid envelope makes it less stable)
what is glycoprotein associated with a virus?
anchored into the envelope and allows attachment to a host cell
what does the viral components need to do in order for the envelope to have viral proteins for cell attchement?
assembly of the cellular membrane
what are the steps of viral replication?
- electrostatic interactions/attachment
- receptor-meidated endocytosis
- fusion of viral and cellular envelopes
- uncoating of viral nucleic acid
- viral protein synthesis and genome replication
- packaging of viral genome into viral proteins (assembly)
- viral budding and release
what is cytopathic effects?
when the cells begin to die
what does viral culture measure?
measures whether infectious virions are present
what does PCR measure?
whether viral DNA/RNA is present
what does and antigen test measure?
measures whether viral protein is present
what is the most abundant polymerase found in the mammalian host?
DNA-dependent RNA polymerase
what does acyclovir inhibit?
inhibits herpesviral DNA polymerase
what do DNA viruses depend on for replication?
they use DNA polymerase for replication
(this is bc fewer mutations are introduced and therefore they are more genetically stable than RNA viruses)
what are the two main things that viruses need to do?
- make viral genome
- make viral proteins
what is Baltimores classification?
-to get to DNA you need to get to mRNA
by convention if you have a piece of RNA that can be directly translated into protein - positive sense
RNA that needs to undergo reverse complementarity to become positive sense before it can be translated- negative sense
what is group 1 of Baltimores classification?
dsDNA
-start off with double stranded DNA and to make genome you need to go from DNA to DNA (DNA-dependent DNA polymerase)
-mRNA is transcribed by DNA-dependent RNA polymerase
A. inhibitor of DNA dependent DNA polymerase
what is group 2 of Baltimores classification?
ssDNA (extra step ss–> ds)
-the genome is replicated by DNA polymerase
-DNA has to be double stranded to act as template for mRNA synthesis, so ssDNA turned into dsDNA prior to mRNA synthesis
what is group 3 of Baltimores classification?
dsRNA
-genome is replicated by RNA-dependent RNA polymerase
-the negative sense RNA strand blocks translation of the positive sense, so first have to use the RdRp to produce mRNA before protein synthesis can occur
what is group 4 of Baltimore classification?
positive ssRNA
-genome is replicated by RNA-dependent RNA polymerase (RdRp)
-genomic RNA can be directly translated while also going through negative intermediate to synthesize more templates for mRNA
what is group 5?
negative ssRNA
-genome is replicated by RNA-dependent RNA polymerase (RdRp)
-genomic RNA can NOT be directly translated, must produce mRNA before synthesis
negative ssRNA vs positive ssRNA
-negative genomes need to bring in a protein copy of RdRp to synthesize mRNA
-positive ssRNA genomes do not require a protein copy of RdRp bc genomic viral RNA can translate directly to make the RdRP in the host cell
what is group 6?
(+) ssRNA retroviruses
-genome is replicated by reverse transcriptase (RNA to DNA which then integrated into host genome)
-mRNA is synthesized from integrated viral DNA
-retroviruses derive their name bc ability to reverse the flow of genetic info (RNA to DNA)
what is group 7?
gapped dsDNA
-genome is replicated by DNA polymerase and reverse transcriptase
-ssDNA has to be repaired first into dsDNA before mRNA synthesis and protein production
