Viruses Flashcards
Identification
What is the first discovered virus? Who discovered it?
Tobacco Mosaic Virus (TMV)
Dmitri Ivanovsky
Define
What is a virus?
- obligatory intracellular parasites
Extra
* macromolecular aggregates
* composed of inanimate particles that by themselves, cannot reproduce, metabolize, or carry functions associated with life.
Explain
Are viruses alive?
It depends!
* Outside hosts: virion, inert/inactive
* Once they enter the body, they begin to display the characteristics of life (reproduction, evolution)
Identification
Virus particle when found outside hosts
Virion
List
Viral characteristics
4
- Has a nucleic acid that functions as their genome (DNA or RNA)
- Has a capsid: Protein coat/shell that encloses genome
- Capsid can be enclosed within an outer envelope made up of lipids, proteins, and carbohydrates and taken from the host cells
- Have surface proteins along its surface
Identification
subunits that compose capsid
Capsomeres
Identification
capsid + viral genome (DNA/RNA)
nucleocapsid
Identification
- allows virus to interact with receptor proteins in their host cell → leads to infection
- determine the virus targets since they interact with specific receptors on the surface of their host cells
surface proteins
Identification
What is the spike in SARS-Cov-2 (causes COVID-19)?
Spike glycoproteins
Identification
In SARS-Cov-2 (causes COVID-19), what enzyme does its spike bind to?
angiotensin converting enzyme 2 (ACE2)
Identification
What are the 4 key characteristics for viral classification?
according to the video
- Genetic material
- Target host
- Capsid shape
- Enzymes they produce
Explain
What is the difference between an enveloped vs a naked virus?
Enveloped virus: nucleocapsid + outer envelope + spikes + surface proteins that help virus adhere to host
Naked virus: nucleocapsid + surface proteins
Identification
What is the virus with the most base pairs? How many base pairs does it have?
Pandoravirus, 2.74M base pairs
List
What are the different characteristics of the genetic material in a virus?
3
- Single-stranded/Double-stranded
- Linear/Circular/Segmented (Arrangement)
- Plus Sense/Minus Sense
T/F [Bonus: If false, what is wrong?]
In viruses, DNA can be single-stranded.
True
Although DNA is usually attributed as double-stranded, it can be single-stranded too.
Note: RNA can ONLY be single-stranded
List
How can viruses be arranged? What are these arrangements similar to?
3
- Linear: like humans
- Circular: like bacteria
- Segmented: Unique to Influenza
Explain
Why is influenza hard to kill?
Can escape antibodies after vaccination bc nucleic acids mutate a lot
List
What processes does influenza undergo that makes them stronger?
3
Antigenic drift
* accumulation of mutations
* Change arrangement of RNA → new strain
Antigenic shift
* 2 influenza viruses are on 1 individual
* RNA of 2 viruses mix
Alters surface proteins → become undetectable by present antibodies
Explain
How does a plus sense virus turn into viral proteins?
same base sequence as viral mRNA → translation → viral proteins
Explain
How does a minus sense virus turn into viral proteins?
Viral replication: complementary to viral mRNA → conversion → plus sense RNA counterpart → translation → viral proteins
Identification
What is a plus sense virus that goes through a different process?
Family Retroviridae
Explanation
How does the Family Retroviridae convert the virus to viral proteins?
plus sense single stranded RNA → reverse transcription → DNA → transcription → mRNA → translation → viral proteins
Identification
What virus has the smallest size?
Polio virus (28 nm, around the size of a ribosome)
Identification
What virus has the largest size?
Hint: It is so big that it can be viewed under a light microscope
Pithovirus
List
What are the kinds of capsid shape? What symmetry do they have?
3
- Helical: rod-shaped symmetry
- Icosahedral: spherical symmetry
- Complex: Head + tail bacteriophages
Identification
- capsid shape with rod-shaped symmetry
- Length: genome length
- Width: Capsomere arrangement length
- Ex.: Tobacco Mosaic virus, Ebola virus, Rabies virus
helical
Identification
- capsid shape with spherical symmetry
- 20 triangular faces, 12 corners
- Ex. poliovirus, herpes, influenza; many plant, animal, bacterial viruses
icosahedral
Identification
- capsid shape with Head + tail bacteriophages
- Icosahedral head
- Helical tail
- Ex. T4 bacteriophage
Complex viruses
List
What kinds of assembly do viruses go through?
2
- Self-assembly: assembly info is in their genomes
- Assisted assembly: need assistance of host cell’s chaperone proteins
List
What are the subviral particles that cause disease?
2
viriods, prions
Identification
- Naked, single-stranded, cirular RNA with hairpin shaped structures
- enters through a wound bc it can’t interact w/ host cell receptors
- attributed to severall plant diseases
Viroids
Identification
Give an example of a viroid disease.
What kind of symptoms do viroid diseases produce?
____ related symptoms
Cadang-cadang disease, growth related symptoms
Explain
How do viroids infect the host?
- enters through a wound
- relies on host cell machinery to replicate
- moves across cells through plasmodesmata
Extra: they usually mimic or interfere with host regulatory RNAs that function for growth
Identification
How viroids move from one cell to another
plasmodesmata
Identification
- cause transmissible spongiform encephalopathies which are uncurable neurodegenerative diseases
- no DNA or RNA
- can destroy the brain & other nervous tissue
Prions
Identification
What does prions stand for?
proteinaceous infectious particles
Explain
What is the mechanism of prions?
- Prion host cells (ex. Human cells) have Prion Protein (Prnp - gene)
- When Prnp is expressed → prion protein cellular (PrPC - protein)
- Prion Protein Scrapie (PrPSc - Pathogenic Prion) enters body → more PrPC becomes PrPSc by misfolding
- Amyloid formation
- Leads to transmissible spongiform encephalopathies (Alzheimer’s, Huntington’s, Parkinson’s, Type II Diabetes)
Identification
- uncurable neurodegenerative diseases
- what prions are responsible for
transmissible spongiform encephalopathies
Identification
- insoluble crystalline fibers
- what prions form
- causes transmissible spongiform encephalopathies
amyloids
Fill in the blank
Viroids are ____ that cause ____ diseases in ____, while
Prions are ____ that cause ____ diseases in ____.
RNA, growth-related, plants
proteins, neurodegenerative (nervous tissue related), animals
