viruses Flashcards
where is the only place a virus can reproduce
in host cells
T or F: viruses are alive
false; they’re not alive because they don’t meet all the requirements of living organisms
list the reasons why viruses aren’t alive
they’re acellular, don’t respond to stimuli, don’t undergo metabolic reactions, and they don’t maintain internal conditions through homeostasis
what nucleic acid type(s) can viruses have
ss DNA or ss RNA
ds DNA or ds RNA
what surrounds the genome of a virus
a protein coat called a capsid
what is a capsid
a protein coat that surrounds the genome of a virus
what is the name of the proteins that make up the capsid
protomers
what are the three types of capsid symmetry
helical, icosahedral, complex
describe helical capsids
the protomers self-assemble in a helical/spiral arrangement to produce a rod structure
give an example of a virus with helical capsid
tobacco mosaic virus
describe icosahedral capsids
a polyhedron with 20 equilateral triangular faces and 12 vertices
give an example of a virus with an icosahedral capsid
human papilloma virus (HPV)
describe a complex capsid
they have complicated structures and may possess tails and other structures
give an example of a virus with a complex capsid
T4 bacteriophage (they infect E coli)
what layer do some bacteria have that surrounds the capsid
viral envelope
what is the viral envelope made of
protein, lipids, and carbs
what do some enveloped viruses have that project from the surface of the envelope
spikes
what is a virus called that doesn’t have its capsid covered by an envelope
naked or nonenveloped
advantage to having an envelope?
helps the virus to evade the host’s immune system
disadvantage to having an envelope?
more sensitive to environmental conditions (ie antimicrobial agents)
what is the highest taxonomic group for viruses
family
list 4 ways viruses are grouped into families
type of nucleic acid, if it has an envelope or not, symmetry of the capsid, dimensions of the virion (fully formed virus)
what do order names end in
virales
what do family names end in
viridae
what do subfamilies end in
virinae
what do genus names end in
virus
T or F: specific epithets are always used for viruses
false; they are not used
since specific epithets aren’t used for viruses, how instead are they named
species names are given by descriptive common names
other than taxonomy, what is another system of how viruses are groups
the baltimore system
describe the baltimore system
viruses are placed into 1 of 7 groups based upon the type of genome they have + their replication strategy
list the 6 steps of the lifecycle of an animal viruses
attachment, entry, uncoating, biosynthesis, assembly, release
describe attachment of an animal virus lifecycle
through random collision, animal viruses attach to their receptors on the host cell’s surface
describe entry of an animal virus lifecycle
- endocytosis (most common), used by enveloped and non enveloped
- fusion, only used by enveloped
describe uncoating of an animal virus lifecycle
separation of the nucleic acid from the capsid
describe biosynthesis of an animal virus lifecycle
the virus takes over the host cell and uses its enzymes + ribosomes to replicate its own DNA and make its capsid proteins
describe assembly of an animal virus lifecycle
everything is put together
describe release of an animal virus lifecycle
nonenveloped: causes lysis to the host membrane = host dies
enveloped: released by budding
how does an envelope protect the virus from the host’s immune system
the immune response is unable to recognize it as forgein
list 3 types of viral infections
acute, latent, chronic
what is an acute infection
rapid onset, lasts for a short period of time
example of acute infection
influenza virus
what is a latent infection
the viruses have the ability to remain formant after the initial infection, and can become reactivated later
example of a latent infection
herpes simplex virus
how is herpes simplex virus reactivated (it’s a latent infection)
due to stress, sunburn, hormones, trauma
other than HSV, give another example of a latent infection
chicken pox
which virus is chicken pox
a herpes virus: HSV-3
what is chicken pox reactivated to form
shingles
what is a chronic infection
these are reactions that occur over a long period of time. Amount of virus gradually builds up. They are usually fatal
example of chronic infection
measles virus
why is measles chronic
in some children, it can lead to an infection of the brain called SSPE (subacute sclerosing panencephalitis; Dawson’s disease)
T or F: some viruses can cause cancer
true
give an example of viruses that can cause cancer
hepatitis B or C, HPV
