lecture 10: viral life cycles Flashcards
what is a virus?
viral genome enclosed in a protective coat
what is the viral genome?
-single or double strand DNA or RNA
-linear or circular
what is the protective coat of the virus?
-capsid
-rod shaped or polyhedral
-comprised of protein subunits called capsomeres
true or false, all viruses have envelopes
false, only some
what is the viral envelope? what does it consist of?
-found in certain viruses
-membrane that covers capsid and is derived from the host membrane
-contains viral proteins and glycoproteins
wha type of parasites are viruses?
obligate
true or false? virus cells are host specific.
true! (example: influenza virus infects cells of the respiratory tract
how do viruses infect specific cells?
specific interactions between viral glycoproteins and host-cell receptors
what are the steps to infection with viruses?
how do viral glycoproteins get into the viral envelope if the envelope is a piece of the host cell’s membrane?
viral glycoproteins are synthesized at ER, and will travel in vesicle to plasma membrane to be picked up by the budding virus. basically, through cell budding
what are the 2 types of bacteriophage life cycles?
1) lytic life cycle (cell lyses)
2) lysogenic life cycle (cell does not lyse)
what type of cells do bacteriophages infect?
bacteria cells
during the lytic life cycle, what is the enzyme produced from the viral genome that digests the bacterial cell wall?
lysozyme
during the lytic life cycle, what destroys the host’s DNA?
the first viral proteins produced destroy the host’s DNA
what are the steps to the lytic cycle?
true or false, the phage DNA circularizes in the lytic and lysogenic cycle
true!
what are the steps to the lysogenic life cycle?
what is the link between the lytic and lysogenic cycle?
During lysogenic cycle, if prophage exists bacterial chromosome, lytic cycle is initiated
what are the bacterial defences against phages?
restriction endonucleases
what do restriction endonucleases do?
they cut foreign DNA that enters the cell
how is the host cell DNA protected from restriction endonucleases?
protected from degradation by methylation
what are retroviruses?
enveloped viruses with a single stranded RNA genome
by what enzyme does the single stranded RNA genome of a retrovirus serve as a template for DNA synthesis
reverse transcriptase
explain the retroviral life cycle
what is a provirus?
when viral DNA is inserted into host cell’s chromosomes for retroviruses
what is an example of a retrovirus?
covid
true or false, prions are viruses
false!
what is a prion?
-a prion is a misfolded form of a protein normally found in brain cells
-once in a cell, prions convert the normal form of the protein to the misfolded prion form (prion causes other normal proteins to fold)
-prions form aggregates (clusters) that disrupt normal cell functions in the brain
-prions act slowly (10+year incubation) and are virtually indestructible
