4 Virology Flashcards
what does it mean that viruses are obligate intracellular parasites?
- cannot live outside living cellular host
- cannot be treated or cured with existing medical therapies
name 3 hosts for viruses
- plants (variegation)
- animals
- bacteria (bacteriophages
how many cell types do viruses affect?
one specific cell type
what are viroids?
- smallest known pathogens
- naked, circular, single-stranded RNA molecules that do not encode protein yet replicate autonomously when introduced to host plants
a viral particle is a ____
viron
viral structure consists of…
- protein coat
- nucleic acid core
- envelope (occasionally)
what is the effect of a viral envelope?
steals plasma membrane from infected host cell, acting as camouflage from immune system
name 3 ways to replicate viruses
- cell culture
- fertilized eggs
- living animals
the protein coat surrounding the nucleic acid core is called a ____
capsid
each capsid consists of identical protein units called ____
capsomeres
what do capsomeres do to viral structure?
bond together and give capsid symmetry
name 2 basic patterns of virus capsids
- helical symmetry
- icosahedral symmetry
helical symmetry
protein subunits and nucleic acid are arranged in a helix
icosahedral symmetry
protein subunits assemble into symmetrical shell that covers nucleic acid-containing core
what are the 2 nucleic acid cores and forms by which viruses are characterized?
DNA and RNA
(double or single stranded)
how many strands are in double stranded DNA?
4
how many strands are in double stranded RNA?
2
what are the 5 levels of viral classification?
- nucleic acid
- symmetry of capsid
- naked or enveloped
- type of nucleic acid
- family name
what is the youngest viral family?
filoviridae
how are hemorrhagic fevers classified?
(eg. Ebola, Marburg, Lassa)
- RNA
- helical
- enveloped
- single stranded
- filoviridae
what is the largest viral family that infects humans?
herpes
what is the most stable viral form?
viruses with double stranded DNA genome
(eg. herpesviridae)
what viral form is most prone to mutation?
viruses with + single stranded genome
(eg. Ebola, HIV)
many viruses that infect mammals are ____
enveloped
all envelopes have a ____
phospholipid bilayer
envelopes arise from…
plasma membrane of infected host cell
lytic infections
host cell fills with virions and bursts resulting in cell death
steps in lytic infection
- attachment
- penetration
- uncoating
- biosynthesis
- maturation
- release
virion attachment
- virus binds to specific receptors on host cell (viral tropism)
- some require co-receptors for successful attachment
virion penetration
- adhesion of virus to host receptors
- engulfment into vesicle
- viral RNA released from vesicle
what is virion uncoating and what are 3 locations it can occur?
uncoating = removal of capsid
- at plasma membrane
- in cytoplasm
- at nuclear membrane
virion biosynthesis
develop provirus (partial host DNA + viral DNA)
virion maturation
involves moving newly made virions to specific sites in cell for intracellular trafficking and assembly
what is the most important part of virion assembly?
placement of viral genome inside the capsid
virion assembly
- virion assembled while viral genome inside capsid
- viral genome inserted into already-formed capsids
