Virus Flashcards
Define a virus
non-cellular, obligate intracellular parasites. Must use the host cells machinery to replicate.
Define a capsid
Protein coat that protects viral genome from the environment and acts as a vehicle for transmission
Define a virion
Fully developed infectious virus particle.
Define an envelope
A structure mostly composed of phospholipids; covers the capsid, may include spike that helps with attachement. Envelope is formed when the virus is released through budding. (looks like exocytosis)
Define a host range
A spectrum of organisms or cells that a given virus can infect.
How is a host range determined?
Determined by the host cell attachment sites and cellular factors
How is a viral species defined?
A group of viruses sharing the same genetic information, and host range.
How are viruses names?
Species common name-subspecies designated by a number.
What are some characteristics of Virion genome?
Can be either Single stranded or Double stranded RNA, or DNA. Genes are purely for the synthesis of a new virion, with a few enxymes needed for early infection steps. Everything is supplied by the host cells. (polymerase, ribosome, ATP, tRNA.)
Define the lytic cycle
Replication cycle of some viruses. Ends with lysis of the host cell.
Define the Lysogenic cycle.
Replication cycle of some viruses. Virion genome is incorperated into the host cell, through recombination. Doesn’t immediately take over the cell; the genes are repressed by virus derived repressor proteins, and bind to the prophage operators. Waits for a UV, or chemical signal.
What are the steps of the lytic cycle?
1) Attachment: Virius attaches by tail fibers to host cell.
2) Penetration: Lysozyme opens cell wall, and tail sheath injects the NA into the cell.
3) Biosynthesis: Host cell processes are halted. Production of virus NA and proteins take over.
4) Maturation: Assembly of virion.
5) Release: Lysozyme breaks the cell wall and causes new virions to release.
Define a temperate phages
“A virus that is capable of ““choosing”” between a lytic cycle and lysogenic cycle.”
Define a prophage
Virion DNA that is inserted into the host cell’s chromosome.
What are some characteristics of SARS-Cov-2 virus?
SARS: Severe Acute Respiratory Syndrome. Single stranded RNA. Enveloped, with S-spikes. Has a lytic replication cycle.
Why are viruses not considered living?
They are unable to replicate on their own.
They do not metabolize their own energy, relys on the host cell.
What structure would help a parasitic protozoan survive outside of a host for longer?
Cyst
What are some characteristics that protozoan and bacteria have in common?
Both are unicellular
Both have RNA in their cytoplasm
Pathogens can be found in both of these categories
What are some characteristics that are found in protozoans but not in viruses?
Able to synthesize its own proteins
Able to catabolize it’s own nutrients to generate ATP
Contains both DNA and RNA
Classified into domain Eukarya
What type of horizontal gene transfer mechanism may occur during the lytic phage infection?
Transduction
During viral infection, what is needed from the host cell’s resources that the virus will need to take advantage of in order to replicate and produce new virions.
Ribosome, nucleotide, Amino acids, ATP, RNA polymerase, DNA polymerase… pretty much everything else you can think of.
What structure plays a major role in determining the host range of a particular virus?
The spikes on the surface of virions (part of the envelope
Define Antigenic drift
A mutation causes a minor variation in the structure of the spikes of the virus. This change may cause some degree of unrecognizability to the host immune system, that may have been developed from previous infections.
