After Quiz 10 Flashcards
History of viruses
- Overall, how were they discovered (how did they know it wasn’t bacterial, fungal, etc)
they took extract of a diseased plant and put it through a filter with tiny holes that bacteria could not pass through. They theorized that there was an agent causing the disease to fit through
What was important about the work of Reed, Stanley, and Ruska?
- You don’t need to know dates or even which person did what. I want a general flow of the major discoveries
1) viruses can cause disease in humans
– also, viruses can be transmitted by vectors
2) scientists isolated and purified a virus, helping determine what they are made of
3) electron microscope helped visualize viruses for the first time
Major virus properties
- General size? What can they infect? Basic structure?
extremely small; 10-1000x smaller than its host cell
infect all forms of life – bacteria, fungi, protists, plants, and animals
Basic virus structure?
Viruses are essentially protein shells that contain a genome
What is meant that viruses are obligate intracellular parasites?
Viruses cannot metabolize on their own, and therefore need to use resources from a living cell. More specifically, a virus needs to be inside of a cell to make more of itself
What are all the varieties in viral genomes?
- use either DNA or RNA
- can be single-stranded or double-stranded
- can be linear or circular
What is the difference between + sense and – sense single-stranded RNA viral genomes?
- with positive sense RNA, ribosomes can bind directly to the genome and translate it into protein
- with negative sense RNA, the genome is opposite sense of mRNA, so it needs to make a complementary and sense copy in order for translation to occur
In having an RNA genome, what special ability must viruses have to replicate its genome?
They need RdRp in order to make more RNA
What is the capsid and what does it do
the capsid is a protein shell that protects the genome
Capsid organization : know capsomer, protomer, capsid, and nucleocapsid
- individual proteins aggregate into small protomers
- protomers assemble into capsomeres
- protomers and capsomeres together form a capsid
- nucleocapsid is the name for the capsid and genome together
What are the three major shapes that capsids can adopt and how do they differ structurally? How is the genome packaged into different types of capsids?*
1) helical : capsid proteins self-assemble around the shape of the genome and form a structure similar to the shape of a straw; assembled with the genome
2) icosahedral : 20 faces, each an equilateral triangle, capsid often forms before the genome is assembled
3) irregular : have a complex structure or their shape is not regular
What is the viral envelope, where does it come from, what is its function, what does it contain, and how is it obtained?
The viral envelope is a phospholipid membrane that surrounds the nucleocapsid, acquired from a host membrane
– obtained when a virus buds through the host membrane
- functions to protect the nucleocapsid
- contains viral glycoproteins that are used for attachment to host cells, also a few host proteins
What is the viral matrix, where is it located, and what does it do?
The matrix is a protein later between the nucleocapsid and envelope present in enveloped viruses
What are the three major criteria for classifying viruses?
1) genomic structure : RNA/DNA, ss/ds, single molecule/segmented
2) capsid structure
3) presence of an envelope or not
What are the three outcomes of a standard viral infection?
1) Lysis : host cell is killed during infection and new viruses are released
2) virus replicates, no cell death or permanent changes
3) viral genome integrates into the host genome or permanently establishes itself elsewhere in the cell, which can lead to a latent infection
