Micro-organisms: Viruses Flashcards
(12 cards)
Viruses
They are small parasites that lack the ability to undergo replication, transcription, translation or survive outside a host cell.
Viruses lack the capacity of … which is the ability to …
homeostasis
regulate and sustain their internal environment
Structure of viruses
nucleic acid - either double stranded DNA or single stranded RNA
Nucleic acid surrounded by capsid
Outer membrane = lipid envelope (obtained via budding from the host cell)
Attachment proteins (lipoproteins)
Integrase - viral enzymes
Nucleocapsid ( nucleic material and capsid together)
How do viruses replicate
Large DNA viruses can encode their own replication and transcription factors
RNA viruses require RNA polymerase from host cells to replicate, they need them for transcription.
Viral replication cycle (5)
1) Attachment - viruses bonds to host cell with attachment proteins
2) Viral entry - viral genome enters the host cell and injects itself into the host cell DNA
3) Synthesis - host cell machinery manufactures the viral proteins, meaning they can now make the viral nucleic acids
4) Assembly - new virus is formed from the components
5) Release - newly formed viruses bud off from the host cell in a process called lytic release where the new virus leaves with a layer of the host cell’s surface membrane
Viral replication means…
the host cells dies, hole in membrane/ can’t properly replicate?
which viruses are linked to cancer?
Oncoviruses
How do oncoviruses work?
they produce proteins that inhibit or deteriorate the function of tumour suppressor genes = cells now grow uncontrollably
Clinical significance of viruses:
HIV - a retrovirus that dampens immune system by depleting T-lymphocytes
Cancer
Viruses that infect bacteria are…
bacteriophages
Virion
the inactive form of a virus outside a host cell with a core of RNA and a capsid
Reverse transcriptase
an enzyme that makes DNA from RNA
