Chapter 6: Acellular Pathogens Slides Flashcards
What are the two things a virus must have?
Genetic material
Protein Coat
True or False: Viruses are infectious, acellular pathogens?
True
True or False: Viruses are obligate intracellular parasites?
True
What is host specificity?
What specific hosts viruses can effect.
What is cell specificity?
What cell types they can effect
What is tropism?
The action of a virus targeting a certain cell type.
True or False: Viruses can be made of DNA by not RNA.
False: Viruses can contain DNA or RNA.
What surrounds a protects the genome of viruses?
A protein capsid.
What can surround the virus and is made of host plasma membrane?
An envelope.
Why do viruses need host cells?
They lack the necessary genes for reproduction.
What are the three different viral shapes?
Helical
Polyhedral
Complex
What is the most common shape for human viruses?
Polyhedral
What is a complex virus shape?
Anything that not is helical or polyhedral.
What is a capsid?
Assembled by individual proteins, protects the virus.
What is a capsomere?
Subunit of a capsid?
How is a capsid structured?
Assembled by individuals proteins associated into progressively larger subunits.
What two aspects of a virus play a role in host recognition?
Envelope proteins and glycoproteins.
True or False: Enveloped viruses are more fragile than naked viruses.
True.
What is the viral envelope made out of?
Phospholipid bilayer and proteins.
Some proteins are virally coded glycoproteins (spikes).
True or False: Viruses can have a single-stranded or double-stranded genome.
True.
What is the order of replication normally?
DNA to RNA to Proteins
What are the most common types of genomes for viruses?
ssRNA and dsDNA.
What is special about virus RNA?
It can be positive sense (mRNA) or negative sense.
Why is the structure of the genome important?
It heavily dictates the replication cycle of the virus.
What are the four things viruses can be classified on?
Type of nucleic acid
Presence of an envelope
Shape
Size
True or False: Relationship among viruses is well understood.
False
How have viral genera been organized?
Into families.
What are the 6 stages of viral replication?
Attachment
Entry/Penetration
Uncoating
Biosynthesis
Assembly
Release/Budding
What is initial attachment?
Involves viral surface molecular structures and host cell molecular structures.
Tropism.
What is entry and what are the two different kinds?
Passage of virion into host cell.
Receptor-mediated endocytosis, membrane fusion
What is receptor-mediated endocytosis?
Virus binds in place of normal ligand
Tricks cell into thinking it needs to bring the virus inside.
What is membrane fusion?
For enveloped viruses only.
Fusion promoted via viral glycoproteins.
What is uncoating?
When the virus tales off capsid to allow access to genome (RNA or DNA)
What is the goal of the synthesis of the viral genome?
To create genetic material for progeny.
What dictates the synthesis of the viral genome?
The type of virus (genetic material).
Where does viral assembly take place?
Assembly typically occurs in area of cell in which viral genome replication occured.
When does assembly begin?
When necessary protein pieces reach sufficient concentration.
How are naked viruses released from the host cell?
They are released upon cell death/lysis.
How are enveloped viruses released from the host cell?
They are released through budding/exocytosis.
What kind of enveloped do viruses get when leaving through budding?
Membrane derived envelope.
What kind of envelope do viruses get when leaving through budding?
Membrane derived envelope.
What kind of envelope do viruses get when leaving via exocytosis?
ER/Golgi dervied envelope.
What type of nucleic acid must all viruses make?
mRNA.
What do DNA viruses require for genome replication?
Host derived RNA polymerase.
Where does genome replication take place in host cells?
The nucleus.
What is negative sense?
It must convert the genome into positive sense for translation.
What intermediate does ssRNA(+) go through?
A DNA intermediate that is achieved using a reverse transcriptase that is RNA-dependent DNA polymerase.
After dsDNA is made, where does it go?
It is inserted into host chromosomes that is achieved by viral integrase.
What are viral mRNAs and + sense RNA progeny strands transcribed by?
RNA polymerase.
How do viruses cause transformation/cancer development?
They cause a disruption of growth signals.
Cells do not stop growing a tumors form.
How do viruses cause a lytic infection, and what is it?
The death of host cell through lysis,
The infection is released, but body will destroy it.
How do viruses cause a persistent infection, and what is it?
The slow release of virus without cell death.
The host cell can still make virus.
Hard to get rid of.
How do viruses cause a latent infection and what is it?
When the virus is present but not replicating.
Waits until you’re sick to replicate.
The genomes from the virus are inserted into yours so cells just keep genomes.
What is cell fusion?
When the cells fuse together.
Ex: Mad Cow Disease
What happens when no progeny is released from the cell, but a virus enters?
Non-permissive cell
Infection with defective virus
Cell death before viral assembly occurs
What is the typical result of a lytic infection?
Typically the result of a productive infection.
Why does the host cell die in a lytic infection?
Host cell dies typically die to overwhelming amount of cells resources consumed or shutoff by the virus.
What does the virus disrupt in a lytic infection?
Disrupt DNA and RNA synthesis
Disrupt lysosome function
Disrupt protein synthesis
Induce apoptosis.
What kind of viruses most commonly create tumors?
DNA viruses
What part of the outside of the cell is changed in a lytic infection?
The antigenic specificity of the outside of the cell may be altered.
What does working with viruses require?
Culturing requires living cells.
How can we tell if the virus killed the cells in a culture?
Virus-induced death of cells result in a clear zone (plaque).
Why do we inject viruses in eggs to study them?
Many parts of an embryonated egg will allow viral replication.
Influenza immunzation.
What are viroids?
Circular pieces of self-replicating RNA (no coat).
What are virusoids?
Non-self replicating ssRNA.
Requires a “helper virus”
What are prions?
Made of protein
Can replicate even without DNA and RNA
All affect the PRNP protein
What do prions cause?
Neurodegenerative diseases
Ex: Creutzfeldt-Jacod Disease (CDJ)
Made Cow Disease
Chronic Wasting Disease
What are the three ways prions are acquired?
Genetic, Sporadic, and Aquired.
Is there a cure for prion-caused diseases?
No, they are always fatal.
What do these prion-caused diseases caused?
Accumulation of PrPsc causes brain tissue to take on “spongey” appearance
Loss of coordination and muscle movement
Cognitive issues.
