viruses Flashcards
what are viruses?
small particles that infect living cells to replicate
are viruses alive?
classified as non-living
where are viruses said to have originated from?
fragments of genetic material
why do viruses blur the line between life and not life? (name 4/8 reasons)
do not maintain homeostasis
is not made of cells, no organelles
has different levels of cellular organization (nucleic acids, capsids)
does not grow
kind of reproduces - replicates
unknown whether responds to stimuli
uses host cell’s energy and material
mutates and evolves, adapts to surroundings
what are capsids made out of?
capsomere
what is a viron?
a singular virus particle
what comprises a virion?
genes and capsid
what is a capsid?
a protective protein shell
why don’t antibiotics work on viruses?
viruses don’t perform basic life processes, the medication targets those processes in bacteria
how does antiviral medication work?
interferes with replication/viral synthesis, binding + release
what is a prion?
an abnormally folded, infectious, brain protein
how are prions thought to be spread?
food
what do prions cause?
degenerative brain diseases (mad cow, kuru)
what is a viroid?
a small infectious particle that infects plants
describe a viroid
no protein coat, only short stretches of RNA
what stores a virus’s genetic information?
nucleic acid core
describe structural differences between DNA and RNA
both made of phosphate + ribose + nitrogenous base, RNA has one more OH
what is a retrovirus?
virus which originally has a genome of RNA, but is reverse transcribed into DNA in the host
what is involved in reverse transcription?
reverse transcriptase, cDNA, DNA polymerase
what is cDNA?
single-stranded DNA made from reverse transcribing RNA
what is a provirus?
virus that has incorporated its genome into the host cell
how is the host cell recognized? (structure)
spike protein/protein spike
on which viruses are envelopes found?
animal viruses
what (on the envelope) helps the virus binds to the host cell
viral proteins
what structure is unique to the bacteriophage?
tail
made of: tube sheath, tail fibres, end plate, spikes
what does the tail of a virus do?
shortens + contracts then injects the nucleic acid core into the cell
how do plant viruses enter?
tiny rips in cell wall
how do animal viruses enter?
endocytosis
name the 4 step process for viral replication
attachment, synthesis, assembly, release
what are virulent phages?
phages that only replicate through lytic cycles
what are temperate phages?
phages that alternate between lytic and lysogenic cycles
what occurs during a lytic cycle at the end? (hint: to the cell)
lysis
what occurs during a lysogenic cycle?
nothing of note, genes do not take over the cell immediately
what does a lysogenic cycle manifest as for the body overall? (think covid)
asymptomatic periods with occasional flare ups
what is another word for viruses in the lysogenic cycle?
dormant - virus co-exists/is integrated into bacterial DNA
what happens if a dormant virus is triggered?
becomes virulent again, moves to lytic cycle
what can trigger a dormant virus?
DNA damage, temperature change, loss of necessary nutrients
how can bacteriophages be helpful? (hint: our bodies)
kills harmful bacteria in our mucus
what is gene therapy?
process in which viruses are used as vectors to carry altered DNA to infected cells
what are vectors?
carriers of DNA/nucleic material into another cell
how do viral-vector vaccines work?
another virus is weakened and genetically engineered such that it can produce viral proteins of another virus in the body
how do nucleic-acid vaccines work?
uses genetic information for a viral protein that triggers an immune response
what is the purpose of vaccines?
build T and B lymphocytes that will remember how to fight the virus (recall: antibody graph w 2 curves)
how do viroids replicate?
host cell makes copies of the viroid - no instructions for protein synthesis
