Viruses Flashcards
What are viruses
Viruses are macromolecular packages that can function and reproduce only within living cells
What is a virion
- a virus that exists outside of cells
- virons are made of a small amount of DNA or RNA and a protein capsule (capsid)
What is a bacteriophage
A virus that infects bacteria
- composed of a nucleic acid molecule that is surrounded by a protein structure
Narrow host range
Only affects one or few species
ex. the human cold and influenza viruses infect epithelial cells of the human respiratory system
Wide host range
Can infect many species such as humans, dogs, bats, racoons, etc
ex. rabies
Types of infections
Lytic: production of virus particles ruptures and kills cell
Non-Lytic: viral DNA is inserted in host genome, cell can survive but often with impaired function
virus mode of action
- once inside the cell the virus hijacks cellular machinery to synthesize nucleic acids and proteins
- new virus particles are assembled
role of reverse transcriptase
enzyme responsible for the conversion of single stranded viral RNA genome into double stranded DNA that is integrated into the host genome
brief life cycle of a virus
- attaches to host cell
- Virion penetrates cell and its DNA is uncoated
- enzymes are synthesized
- DNA is replicated
- mRNA synthesizes new capsid proteins
- Virion matures
- Virion’s are released and ready to infect cells
Envelope virus life cycle
- virus has a lipid coating and comes by forming a vesicle with plasma membrane
- vesicle pinches off and ends up in endosome
- virus developed in cell where DNA is replicated is released by endosome and starts making more envelope proteins
- progeny virus buds off
- cycle goes on until plasma memb is depleted
