ICL 1.1: Intro to Viruses Flashcards
What are the 3 components of medical virology?
- infectious agent
- health interventions
- host defenses
what are the categories of infectious agents?
- viruses
- bacteria
- fungi
- protozoa
- animalia
what is a virus?
obligate intracellular parasites
small, obligate intra-cellular parasites, possessing either a RNA or DNA genome and a receptor-binding protein (capsid/coat) allowing entry into cells
where do viruses replicate?
they replicate only inside the living cells
this is because they use the cellular synthetic machinery for transcription, translation and replication to cause the synthesis of specialized elements called virions that serve to transfer the viral genome, which can be either RNA or DNA, to other living cells
if you put a virus in a petri dish, nothing will happen!
is the viral genome RNA or DNA?
DNA or RNA: it can be either!!
viruses use cellular machinery to synthesize virions that serve to transfer the viral genome, which can be either RNA or DNA, to other living cells
**there are no bacteria with RNA genomes
what is the infectious form of a virus called?
virion
virions are either enveloped or non-enveloped (naked)
what are the 2 distinct stages/forms of a virus?
- non-infectious form = virion
2. non-infectious form of virus = intracellular form of virus represented by its genome
what are the components of a virion?
- genome
- capsid
- matrix
- envelope
what are the two types of virions?
virions are either enveloped or non-enveloped (naked)
enveloped viruses are sensitive (inactivated) to
organic solvents, detergents
what inactivates enveloped viruses?
enveloped viruses are sensitive/inactivated to organic solvents/detergents
what is the capsid of a virion?
a protein shell that surrounds the genome
the RNA and DNA need to be protected so viruses make a protein shell to protect it
a capsid can have many shapes!
what are the types of capsidss?
- cubic (icosahedral)
- helical
- complex
what is the matrix of a virion?
matrix proteins are extra proteins put into the virus that help with infection or boost the replication cycle
they’re proteins inbetween the capsid and the envelope
not all viruses have a matrix!
what is the envelope of a virion?
its a lipid bilayer with a glycoprotein external layer surrounding nucleocapsid
enveloped viruses have a lipid bilayer outside the capsid protein that contains the viral envelope proteins (these have receptor-binding functions)
some viruses have envelopes and others don’t – viruses without envelopes are called naked
so it goes genome –> capsid –> envelope from inside out
what is a nucleocapsid?
genome + capsid
can you tell which virus something is from the microscope image?
not always
sometimes the image is diagnostic like with HIV because it’s really distinct
but other times you can’t because like influenza looks like Ebola
so images can be helpful but not always
what is the name of the viral structure composed of
the genome enclosed in a protein coat?
nucleocapsid
genome + protein shell
the nucleocapsids of viruses without envelopes are the virion structures of these viruses (also called naked virions)
list the DNA virus families
SMALLEST
1. parvoviridea
- polyomaviridae
- papillomaviridae
- adenoviridae
- ————————— - herpesviridae
- poxviridae
BIGGEST
1-4: naked
5-6: enveloped
which DNA virus families are naked virions?
- parvoviridea
- polyomaviridae
- papillomaviridae
- adenoviridae
which DNA virus families are enveloped virions?
- herpesviridae
2. poxviridae
what are the categories of RNA viruses?
- positive RNA
- double-stranded RNA segmented
- negative RNA
which virus families are positive RNA viruses?
- picornaviridae
- caliciviridae
- hepeviridae
- ————————- - flaviviridae
- togaviridae
- coronaviridae
1-3: naked
4-6: enveloped
which virus family is a double-stranded RNA segmented virus?
reoviridae
it’s a naked virus!
which virus families are negative RNA viruses?
MONONEGAVIRALES
1. rhabdoviridae
- paramyxoviridae
- filoviridae
- bornaviridae
SEGMENTED
5. orthomyxoviridae
- bunyaviridae
- arenaviridae
**these are all enveloped virions!