W2-lecture 2: Infectious particles Flashcards
T or F : viruses are considered living entities.
False, viruses rely on the host cell for energy, metabolic intermediates, and protein synthesis, and so they are obligate intracellular parasites
What are the host cells of viruses
all the group of cellular organisms (archaea, bacteria and eukaryotes)
What is the name of the inert infectious particle
virion
What is the general structure of the virus?
nucleic acid (ARN + ADN) + a protein coat
T or F : There is two types nucleic acid found in the virion of any given virus
false
What are the three shapes of virus ?
- helical virus 2. polyhedral virus 3. complex virus
T or F : every virion contains an enveloppe
False, the bacterial viruses are naked while the animal viruses contain an envelope.
T or F : in some cases, the virus can come with ribosomes and some building blocks and energy.
false, In all cases, the host cells supply the building blocks (nucleic acids, amino acids), the machinery (ribosomes) and the energy required to produce new virus particles.
What are the protein subunits that makes up the capsid?
the capsomeres
What is the most common sape of the polyhedral shaped virus
The icosahedron
What is a capsid?
it is a protein coat around the nucleic acid of the virus. It is made of capsomere (protein). The capsid and the nucleic acid is what makes the nucleocapsid
What determine the shape of the virus?
the nature of the capsomere.
What are the most complicated viruses in term of structure?
The bacteriophages (complex viruses)
T or F : the bacteriophages T4 can’t infect the gram negative bacteria.
False, because they recognize the LPS layer that is only found in gram negative bacteria. So, they can’t infect gram positive bacteria.
T or F : The virion interacts with receptors on the cell wall of the host. If there is not that specific receptor, the virus can’t attach and infect the cell.
T
What are the receptor of the bacteriophage T4?
They LPS membrane
What are the two pathways of infections
Lysogenic pathway and lytic pathway
What happens in the lytic pathway of infection
In a lytic infection, the virus redirects the host cell’s metabolism from growth to support virus replication and the assembly of new virions.
What happens during the lysogenic pathway of infection?
lysogenic infection; in this case, the host cell is not destroyed but is genetically altered because the viral genome becomes part of the host genome (lysogeny).
What is a prophage?
The viral genome that has been incorporated into the host genome and is not expressed because of phage encoded repressor proteins.
What is the method to look at viruses on agar plates
The plaque assay is used. The viruses are mixed with a permisive host and can be seen has plaques (lyse of cells) on the agar after incubation.
What are viroids
Viroids are closed circles of single-stranded RNA containing 240-380
nucleotides.
What is the cause of cadang cadang disease or potato spindle tuber?
viroids
What are prions?
one prion (protein : PrPSc) that induces the wrong folding of normal prions in neurons. (PrPC) leading to accumulation.
