Lecture 10 - Viruses Flashcards
what are some types of viral diseases?
flu, ebola, HIV
what is the size of a virus relative to a bacteria?
it is smaller than bacteria
is a virus a virion? what is a virion? and an example
yes, it is non-living and non-replicating outside the host cell. example: on a door-knob or in blood
are viruses obligate intracellular pathogens?
yes, they can’t survive outside of a cell and they cause diseases
can you see a virus with a light microscope?
no
can viruses infect all forms/domains of life?
yes
what are the domains that viruses infect?
-Bacterial (bacteriophages)
-Archaeal
-Eukaryotic (animal and plant viruses, etc)
is the host range that viruses infect specific or broad? is there an exception?
the host range is usually specific. One exception is Rabies, it has a broad host range
what are the two parts of the virus structure that is always present?
- Genome (nucleic acid core)
- Capsid
what is one part of the virus structure that is not always present?
The envelope
what is within the viruses’ genome/nucleic acid core? does it have DNA or RNA, and is it single-stranded or double-stranded?
-it has either DNA or RNA
-it can be ss or ds
how does the virus being ss or ds help us to detect a virus?
it helps to detect a virus because it we see a ds RNA, we know its a virus
how many genes are present within the genome of viruses? what do they code for?
only a few genes - they code for the viral structure
within the genome of the virus, how does it replicate?
it replicates using the metabolic machinery of the host, because the virus only has a few genes. So they use the genes of the host (our ribosomes, glycolysis, etc.) to replicate.
why are the genome’s within a virus an exception?
Every living cell has DNA as its genome. A virus is an exception because it can have DNA or RNA. All viruses have a genome.
within the capsid of the virus, what is present?
it has a protein coat that is always present with protein spikes that are not always present
what are the protein spikes on the capsid?
they are proteins of the surface
what does the capsid of the virus serve to do?
it protects and attaches
is the viral shape based on the capsid? what are the three shapes?
yes
1. icosahedral: flu, polio, norovirus
2. Helical (filamentous): ebola, rabies
3. Complex: bacteriophage
what is the macromolecule that the capsid is made up of?
protein
what is the envelope made out of in viruses?
a lipid bilayer with protein spikes (that help with attachment)
where is the lipid bilayer of the envelope taken from?
it is taken from the plasma membrane of their host cell
what does the envelope serve to do?
protects and attaches
what are examples of viruses that are enveloped?
HIV, SARS-CoV-2
what is a naked virus?
a virus without an envelope
why are enveloped viruses easier to kill?
because the lipids can be dissolved easier with alcohol, etc.
what does the envelope surround?
it surrounds the protein coat
what is the classification of viruses based on?
on their structure, for example do they have DNA, or RNA, are they ss or ds, etc.
do the viruses species name use binomial nomenclature?
no
what are the viruses named based on?
-Appearance: Coronavirus
-Location: Ebola
-Disease it causes: HIV
in SARS-CoV-2, what is the genome?
ss RNA
what types of proteins are present in SARS-CoV-2?
Nucleocapsid protein (N)
Spike protein (S)
Envelope protein (E)
Membrane protein (M)
does SARS-CoV-2 have an envelope? What is it made out of?
yes:
-lipid bilayer
-Spike protein (S) - corona (crown) of spikes
what is the spike protein?
it is a protein that binds to our cells and helps to attach to our cells
what vaccine is the spike protein present in?
in the mRNA vaccine
how does a typical DNA virus replicate?
- Attachment (attaches to the surface of a host cell to get inside via spike proteins).
- Penetration (gets inside the cell)
- Uncoating (the genome gets outside of its capsid coat).
- Synthesis (makes more genome and proteins for the capsid*. the viral DNA/RNA is replicated, and some viral proteins are made).
a. DNA to DNA (DNA -dependent DNA polymerase).
b. DNA to RNA to proteins using RNA polymerase. - Assembly (takes the genome and covers it with the capsid*? coat).
- Release
If the following are templates and products for virus replication, what are the enzymes used?
1. DNA to DNA
2. DNA to RNA
3. RNA to RNA
4. RNA to DNA
- DNA-dependent DNA polymerase.
- DNA-dependent RNA polymerase.
- RNA-dependent RNA polymerase. (Replicase - the virus has these enzymes NOT the host).
- RNA-dependent DNA polymerase (reverse transcriptase - ONLY in retroviruses).
what are the two types of penetration (the two types of ways viruses enter the host cell)?
- Fusion
- Endocytosis
what happens in fusion?
The envelope of the virus fuses with the plasma membrane of the host cell.
This ONLY happens if the virus has an envelope.
Both of the bilayers fuse together.
Examples of viruses that perform fusion: enveloped viruses such as HIV
what happens in endocytosis?
Both enveloped and naked viruses perform this. Example: the flu virus.
The virus comes into the host cell through membrane pockets and is engulfed. The spike proteins firstly attach.
what are the two types of releases (two ways that the virus is released from the host cell)?
- Lysis
- Budding
what happens in lysis?
The virus cell bursts.
This only happens in naked viruses.
Example: the common cold virus
what happens in budding?
The envelope layer is gained during the release, and the capsid wraps itself in the host cell membrane and pinches off. The virus gets its enveloped layer as they are released.
This only happens in enveloped viruses such as HIV.
how does SARS-CoV-2 replicate?
- Attachment: the S protein (the spike proteins) binds to the ACE2 receptor on the host cell membrane.
- Penetration: Fusion of the viral envelope occurs with the host cell membrane.
- Uncoating: the viral RNA is released in the host cell cytoplasm.
- Synthesis:
- Translation: the ss RNA is used to make viral proteins.
- Replication: RNA-dependent RNA polymerase (RdRP) or Replicase is used. It starts with RNA and makes more RNA. - Assembly: the production of viral proteins and RNA.
- Release: through exocytosis
which of the following in NOT a unique characteristic of viruses?
1. Viral nucleic acid is either DNA or RNA.
2. Virus spikes attach to the host cell receptors.
3. Viral release can occur through lysis or budding.
4. Viruses can replicate on doorknobs.
- Viruses can replicate on doorknobs
What are 3 ways that viruses can interact with host cells? AKA what are the 3 types of infections that viruses can cause in host cells?
- Acute infection
- Chronic (persistent) infection.
- Latent infection.
what is an acute infection?
It is a short-term infection such as the flu, cold, etc. You end up being fine in the end.
-It has a short duration.
-It can have long-lasting immunity.
-Symptoms are the host cell death.
-The virus usually disappears afterward.
what is the chronic (persistent) infection?
The number of viruses is gone after the acute infection period, but they come back.
- t is a long-term infection.
-It is continuous but usually has low numbers.
-The virus can be detected at all times.
-It may or may not cause disease in the chronic phase.
-No symptoms
-You are considered a carrier if you spread the virus. Sometimes you cannot shed the virus (spread the virus).
-Examples: Hepatitis B and C, HIV
in chronic infections, what do you initially have?
you initially have an acute infection, then the viral numbers go down, but we don’t completely get rid of the virus and it resurfaces later.
what is a latent infection?
It is when all the viruses are gone after the acute phase, but the viruses hide in the host cells. It comes back later and the patient experiences different symptoms.
(finish latent infections later).