L19 Infection and Multiplication Flashcards
steps of a virus life cycle
attachment entry synthesis assembly release
what happens during attachment
receptor binding proteins on the virion bind to receptors on the surface of the host cell
where are the receptor binding proteins present on enveloped cells?
on the envelope
where are the receptor binding proteins present on non-enveloped cells?
on the capsid
what could a receptor of a virion be
protein molecule
carbohydrate molecule
examples of protein molecule recpetors
CD4 (HIV)
ACE2 (SARS-CoV-2)
examples of carbohydrate molecule receptors
sialic acid (influenza)
what is a co-receptor (example)
CCR5 for HIV
helps with attachment
A receptor can be ______ for one virus or ______ viruses can have the same _____
unique
multiple
receptor
example of a receptor that is used by Influenza. adenovirus, parainfluenza
sialic acid
are receptors present on all host cells and tissues
no
three entry methods used by viruses
fusion
endocytosis
direct injection
what kinds of virsues tend to use fusion
enveloped
examples of bacteria that use fusion
HIV, bacteriophage o6
what happens during fusion (HIV example)
the spike proteins bind to the receptors on the host cell (attachment)
the envelope fuses with the plasma membrane releasing the capsid into the cytoplasm
endocytosis entry for enveloped viruses
The binding of the spikes to the host cell receptors triggers receptor-mediated endocytosis
-the envelope is degraded by the acidic environment in the endosome and the capsid is released
examples of enveloped viruses that enter through endocytosis
Influenza
corona
endocytosis entry for non-enveloped viruses
capsid proteins bind to receptors that trigger receptor-mediated endocytosis
-the acidic environment alters the capsid which results in extrusion o the viral genome into the cytoplasm
what kind of virus uses direct injection
bacteriophage T4
process of direct injection
bacteriophage attaches and a pore forms
-the release of pressure in the capsid results in the genome traveling down the tail and into the cell
how do viruses enter plant cells
via open wounds
what must a viral genome do once inside the host (synthesis)
replicate
transcribe into mRNA
Translate mRNA into viral proteins
what does genome replication depends on
type/configuration (RNA DNA ss ds)
where does replication occur
nucleus or cytoplasm of the host
what types and configurations of the genome require mRNA to be made
ss/dsDNA and dsRNA
what kind of ssRNA does not require mRNA to be made
positive
how does the translation of the viral genome occur
hijacks host cell, occurs in the same way as host cell
where does translation occur
cytoplasm of host
where does assembly occur
cytoplasm, nucleus and/or plasma membrane
assembly is ______ and tightly _____
complex
regulated
what happens during assembly
viral proteins sequentially react with each other and then with the viral genome to form progeny
what happens to the viral protein being synthesised
some are used to make progeny
some are used to evade host defences
what is the name of the host proteins used to help in virion assembly
chaperones
three mechanisms of release of viruses
lysis
budding
cell to cell
what is required for cell lysis
viral proteins
what kind of viruses use lysis for release
bacteriophage
examples of viral proteins used in lysis
holin
T4 lysozyme
what does holin do
creates holes in bacterial cell plasma membranes
what does T4 lysozyme do
dissolves the bacterial cell wall
An example of a virus that uses budding as a release mechanism
influenza
explain the budding process
- the virus assembles components near or on the plasma membrane and then uses the host cell plasma membrane to form an envelope
- enzyme pinches the bud and releases the encapsulated virus
two ways cell-cell release can occur
through nerve synapses
plasmodesmata
what virus is released via synapses
herpes simplex virus
