16. Viruses Flashcards
what is endocytosis in viruses?
endocytosis - viruses are injested through the celluar membrane, then the envelope it is inside breaks off due to the low PH and the virus is able to reproduce
what is nucleic acid injection?
attaching to the surface of the celluar receptors and injecting only its genome into the cell
what is membrane fusion?
the viruses envelope fuses with the celluar membrane and the viruses contents are emptied into the cell
what is a virus? definiton
they are obligate parasites that can only reproduce within the host cells
what is the basic structure of a virus?
consists of a nucelic acid - can be SS DNA, SS RNA, DS DNA, DS RNA.
enclosed in a protein coat called a capsid
sometimes surrounded by a membranous envelope
what is a capsid and capsomers?
a capsid is the viruses nucleic acid packaged into a protein coat with repeating protein unit. the units are called capsomers
what is a membranous envelope? where does it derive from and what does it contain?
its a lipid envelope that surrounds protein capsids. derives from the plasma membrane of the infeccted cells. contains proteins and glycoproteins of viral and the host
define a host range
each particular virus can infect cells of only a limited number of host species. this is because of a ‘lock and key’ fit between surface proteins and specific receptor molecules
what is a tabocco mosaic virus structure and what nucleotide is it made from?
it infects tabacco plants and is a single stranded RNA nucleic acid with a capsid
what is the adenovirus, what nucleic acid is it made from and what shape is it?
it has double stranded DNA nucleotide and it isocahedral in shape. they include glycoproteins which target eukaryotes for binding.
what is the influenza virus, what nucelotide is it made from and what structures does it have?
has a membranous envelope, glycoproteins and a capsid. made of single stranded RNA
what is the bacteriophage and what is special about its structure?
bacteriophage infect bacteria, they are made of DNA and have a protein capsid head with legs that lanch onto prokaryotes to inject
what are the two different cycles of bacteriophage injecting a celluar host?
lytic and lysogenic cycle
what is the lytic phage?
The virus injects its own nucleic acid into a host cell. The virus’s nucleic acid takes over the cell’s replication and translation mechanisms, using them to make more viruses. specialized viral proteins are dissolve the bacterial cell wall. The cell bursts due to high internal osmotic pressure (water pressure) that can no longer be constrained by the cell wall. This releases viruses into the surrounding environment, where they can go on to infect other cells.
what is the lysogenic cycle?
DNA from bacteriophage inserts into host cell. When DNA replication occurs, the lysogen will replicate and create more lysogens. Daugher cells and DNA carry lysogens and they can spread through the organsims
what are some key differences between the lytic and lysogenic cycle?
In the Lytic Cycle:
Viral DNA destroys Cell DNA, takes over cell functions and destroys the cell in lytic, whereas lysogenic merges with cell DNA
in lytic he Virus replicates and produces reproduces phages. whereas in in lysogenic the virus is replicated using the host.
in the lytic cycle the host cells is destroyed, in lysogenic it isnt damaged
why is there such a rapid rate of evolution in viruses?
mutaions occur in cells and one virus can create thousands of virions which have short generations, therefore natural selection occurs quickly to adapt
they spread easily from dissemination from one organism to another, therefore are able to reproduce
10-20% of cancers associate with viral infections
how can the human and animal health be a consequence of viruses?
high concertations of humans and animals - particulary in farming. viruses can recombinate and adapt. if a person has a human virus that has a host range, however catches a pig virus which has a larger host range, they viruses can recombinate and mutate to deteroite human health.
what is the retro virus?
HIV replication - where there is reverese transcription (RNA is transcribe into DNA). the reverse transcripataes enzyme uses viral RNA as a template for making a complementry DNA molecule.
DNA integrates into a host chromosome, it will hide from the immune system to make viral particles
STUDY IMAGE
what is the difference in celluar reproduction and virus reproduction
viruses can only reproduce when they encounter a host cell. but cells can reproduce by themselves.
what is AZT?
anti retroviral therapy. blocks the transcription of reverse transcriptae. it has a similar struture to thymine. a drug for HIV patients
