viral replication steps
- attachment
- entry
- synthesis
- assembly
- release
attachment
random collision between host cell and virus
- attaches to surface of host cell
what does the virus attach to?
proteins on host cell surface
entry
penetrate into cell, get into cell
- enter host cell and releases nucleocapsid
latent viruses
viruses that enter host cell but does not immediately make the host cell its slave
- delay replication
- still there just not activated
- can get activated eventually
synthesis
host cell stop doing cell work, become slaves to instructions of virus
- nucleic acid replicated & proteins made
release
new vision released from infected cell
assembly
put pieces together, build virus
- capsid, envelope
- replicated proteins & nucleic acids are assembles into nucleocapsid
direct penetration
- bind to protein on host cell membrane surface
- virion opens
- release viral genome
- genetic info in cell
direct penetration: bacterial cells
- have wall, hard to attach to
- attach to flagella and slide down to infect cell
direct penetration: human cells
- attach to membrane proteins, sugars & receptors
another form of direct penetration
injury to cell
- allows entry of virus
endocytosis
- bind to host cell membrane protein
- cell will engulf virus
- double membrane is creates around engulfed virus
- cell triggered to release nuclear capsid & genetic info into cell
endocytosis: influenza
- hemagglutinin spikes bind to protein host cells (sialic acid)
- virus taken into cell by endocytosis
- release genetic info into nucleus
sialic acid
- sugar on cytoplasmic membrane
- influenza virus binds to this
- on epithelial cells in the lungs
membrane fusion
- bind to protein/ receptor on the host cell membrane surface
- membrane fuses and become one
- genetic info in virus moves into host cell
what is specific about membrane fusion?
only works with envelope viruses