Viruses Flashcards
what was the first viruses discovered and how was it discovered?
-tobacco mosaic virus:
discovered by extracting sap from a plant with the disease, giving it to a plant without the disease, and observing that said healthy plants become infected
why are viruses referred to as obligate intracellular parasites?
-viruses cannot make proteins or reproduce on their own. they need a host cell to perform their functions
-because of this, its debated on if viruses are even living organisms
what are the key recognition systems for viruses?
-viral surface proteins interacting with host cell receptors
what are the 3 main structures of a virus?
capsid - protein shell to protect DNA
nuclear material consisting of RNA or DNA
viral envelope - a surrounding of host cell membrane that covers the capsid, obtained after a virus leaves the host cell
what is simple viral reproduction?
-virus enters the host cell
-virus replicates its DNA
-virus uses host cell to create new capsid proteins to protect its DNA
-virus exits cell, assembling themselves and grabbing a piece of nuclear envelope to infect future hosts
what are the 2 modes of bacterial viral reproduction?
- lytic cycle
- lysogenic cycle
-viruses can alternate between one mode of reproduction and the other based on environmental cues
what is the lytic cycle?
-virus enters cell, converts cell into a virus making factory
-when cell is jam packed full of ready viruses, it explodes and releases them
what is the lysogenic cycle?
-virus enters cell and injects its DNA/RNA into the host cell’s DNA
-when the host cell replicates, it now has the viral DNA/RNA in both its daughter cells
what are the main modes of viral defense bacterial cells have?
-surface receptors that will not accept viral surface proteins
-restriction enzymes: cut up and restrict ability of a phage to infect cell through methylation
-CRISPR/Cas system: tldr - cell develops a memory of past infections to fight future ones
what is a provirus?
a latent virus
how do viruses produce symptoms in animal hosts?
-when viruses damage of kill cells, this can be perceived as a symptom by the host
-other reasons include lytic enzymes from lysosomes and toxins in the viral envelope proteins
what are the differences between bacteriophages [bacteria viruses] and animal cell viruses?
-bacteriophages are usually DNA viruses, animal cells are either RNA or double stranded DNA
-animal viruses have several classes & can easily mutate due to poor proofreading skills when injecting themselves into host DNA
what is a retrovirus? what enzyme do these viruses use?
a virus that has a single strand of RNA that it uses to synthesize viral DNA, using an enzyme called reverse transcriptase
-the viral DNA synthesized can be used to create new viruses
what are vaccines?
-harmless / killed versions of a pathogen that stimulates the immune system to kill that pathogen
-immune system remembers how to kill the weakened pathogen and can use this remembering when the real deal shows up
what are prions?
-infectious, misfolded proteins that cause degenerative disease in animals, referred to as transmissible spongiform encephalopathy as an umbrella term
