viruses Flashcards
How does a bacteriaphage infect its host?
The protein capsid contains virus DNA or RNA and it this genome is injected into the cell of the bacteriophage (cell)
What is the most common way phages exit host bacterium?
cell lysis
Describe lysis - for phage exiting host bacterium
endolysin, is coded for in the viral nucleic acid of lytic phage
Endolysin attacks and breaks down bacteria’s cell wall peptidoglycan
Infected bacterium is destroyed as a result.
Describe basic steps of the lytic cycle of bacteriophage
- entry
- releases enzyme to break up host genome
- uses host genome to make it’s own material
- gets assembled
- enough are made lysis occurs
lysogenic cycle
ability of bacteriophage to integrate it’s genome into the host’s cell
- some bacteria have the ability to take their genes and work them into the bacterial chromosome (red-blue double circle)
- produces bacterial and viral DNA
what are viruses made of?
nucleic acid, proteins, and s/m lipids
describe a capsid of a virus
Nucleic acid surrounded by a protective protein coat, called a capsid.
describe envelope of a virus
Some viruses have an outer membranous layer, called an envelope, made of lipid and protein, surrounds the capsid in some viruses.
do all viruses have envelopes?
no
what is a difference between a naked and enveloped virus structure?
an enveloped has an envelope with spikes embedded into it (glycoproteins)
How do viruses differ from living organisms?
Viruses are not living organisms because they are incapable of carrying out all life processes
list characteristics of life that viruses do not conform to
- are not made of cells
- can not reproduce on their own
- do not grow or undergo division
- do not transform energy
- lack machinery for protein synthesis
do viruses have more variety in nature of their genomes than do cells?
yes ; although much smaller than genomes of cells
can be dsDNA, ssDNA, dsRNA, and ssRNA
may be linear and composed of several segments or single and circular
the viral capsid function b/c it has a protein. coat
Protein coat provides protection for viral nucleic acid and means of attachment to host’s cells.
The viral capsid is composed of protein subunits called
capsomeres
capsids are composed of single type of capsomere while others are composed of multiple types; T or F
true
How is the viral enveloped acquired?
Acquired from host cell during viral release; envelope is portion of membrane system of host.
If the viral envelope is taken from an infected cell’s plasma membrane, what macromolecule is the viral envelope primarily made of?
Also contains proteins and virally-coded glycoproteins (spikes).
Envelope’s proteins and glycoproteins often play role in
host recognition
If a virus doesn’t have an envelope,it is considered to be a
naked virus
What is an advantage of having a cell envelope?
- wouldn’t be picked up by immune cells (protection) invisible cloak
- doesn’t require any work - just steals it (steals part of host for it’s own use)
How do viruses exit the cell?
lysis or budding
lysis = naked cell
budding = enveloped cell
How does a virus recognize & attach to its host?
Adsorption
Adsorption
The general phases in the life cycle of animal viruses are adsorption, *penetration, synthesis, assembly, and release from the host cell
why do most viruses infect only a certain type of host?
Specificity due to affinity of viral surface proteins to proteins on the surface of the host cell.
what characteristics bacteroiphages have that are attracted to proteins on the surface of bacterial cells?
bacteroiphages have proteins in their tail fibers (those extensions that look like legs)