Intro to Viruses Flashcards
Size of a virus v.s. a bacteria
viruses are smaller than the smallest bacteria
Viruses (can or cannot) be seen with a light microscope
cannot
What type of nucleic acid do viruses have?
either DNA or RNA, not both
protein coating of a virus is called _____?
capsid
a capsid is composed of identical protein subunits called _______?
capsomeres
some viruses have a lipid/protein membranous outer coating called _______?
an envelope
glycoprotein spikes or projection that protrude from the envelope are called _____?
peplomers
Viruses without envelopes are celled _______
“naked”
What are the two configurations a capsid can have?
icosahedral (cubic) and helical
*
nucleocapsid
*
viron
Viral replication occurs only within a ______ ______
living cell
6 steps of viral replication
- Attachment
- Penetration
- Eclipse
- Replication
- Maturation
- Release
What happens in attachment stage of viral replication?
virus binds to receptors on cell surface
What happens in penetration stage of viral replication?
virus enters cell (by engulfment, though fusion of cell membrane and viral envelope, or by direct passage)
What happens in eclipse stage of viral replication?
Nucleic acid is freed from capsid. Intact viron is not detectable.
The protein coding of the nucleic acid is often inserted into the cell membrane
What happens in replication stage of viral replication?
Host cell manufactures viral nucleic acids and capsid proteins (at separate locations within infected cells)
What happens in maturation stage of viral replication?
New nucleocapsid or virons are assembled
What happens in release stage of viral replication?
New nucleocapsids or virons are released from the host cell (budding or cell lysis)
What are protein substances produced by virus-infected cells that act on infected and surrounding cells to interfere with viral replication.
Interferon
Do interferons act on cell or viruses
on cells NOT viruses
Interferons are most effective on host cells from same ________
species
Why are antibiotics not effective against viruses?
viruses do not have target components
How can viruses be classified?
- nucleic acid type
- virus size, configuration, and composition
- serological cross-reactivity of group antigens `
