Microbiologi 4
Virus vs viron
The virus refers to te entire virus which is an obligatory parsasitic infectious biological particle and a virion is an virus particle
Why do we say virus is an obligate intracellular parasite
Because viruses needs a host cell to replicate and rely on the host for energy, metabolic intermediates and protien syntheis
capsid
A protein shell that surrounds the genome of a particle. It is made up of capsomeres and they can be in different shapes. Icosahedral- spherical, helical viruses- rods, complex viruses- several parts
What is a viral envelope? When during viral replication does the virus get its envelope?
It is the outer most layer of many types of viruses and it consists of a phospholipid bilayer. The virus gets this during the release state
Spikes
Glycoprotein projetions found on the surface of viruses
Viral replication proces
1. Attachment of the virion to the host cell. 2. Penetration of the virion nucleic acid into the host cell. 3. Synthesis of virus nucleic acid and protein by host cell machinery as redirected by the virus. 4. Assembly of capsids and packaging of viral genimes into new virions. 5. Release of new virions from the cell
Susceptible, resistant, permissive cell
A susceptile cell has a functional receptro for the virus. Resistant cell has no receptor and a permissive cell has the ability to replicate the virus
Growth curve for viruses growing in a cell- culture
First step is inoculation and after that the virus will enter the eclipse phase, here the viral genome and proteins will be replicated and translated. Then we have the mutaration phase, this becins when a new synthezised viral nucleic acid molecules beomes packaged inside their capsules. During this phase the number of infectious virions inside the host cell rises dramatically. The eclipse and the maturation phase together comprise the latent period because newly assembled virions are not yet presented outside the cell. At the end of the maturation phase mature virions are released and the virus come in burst size ehich is the number of virions released per cell
Lytic vs lysogenic phase
In the lytic cycle bacterial cells are broken open and destroyed after replication of the virion. As soon as the cell is destroyed the phage progeny can find new hosts to infect. The lysogenic cycle allows the host cell to continue to survive and reproduce
Direct penetration
Used by non- enveloped viruses. The capsid or genome enters the cytoplasm either by the direct injections or after fusion.
Mmembrane fusion
Used by enveloped viruses, the viral envelope merges with the host cell membrane, allowing the capsid to enter the cytoplasm
Endocytosis infection
Used bu both enveloped and non-enveloped viruses. The host cell ingulfs the virus in a vesicle before realising the viral genome
How do non enveloped and enveloped viruses exit the cell
Non- enveloped viruses exit the cell through lysis. Enveloped viruses exit their host cell by budding from a cellular membrane
Persistant vs latent infections
Latent infections virions are not produced and in persistant virions are produced
What can a virus do to a cell?
The host cell can get a persistant infection, virulent infection and transform the host cell into tumor cells
Baltimore classification
It bases the viruses on how they synthesize mRNA
+ssRNA vs -ssRNA
In genetic material processing -ssRNA goes directly to mRNA. +ssRNA needs to transform to -ssRNA first and then to mRNA. In RNA replicase -ssRNA viruses carries RNA replicase in the virion and +ssRNA viruses let the host produce RNA replicase. In transcription +ssRNA is immediately translated to viral proteins but -ssRNA needs to be transcribed into +ssRNA first and then translate to viral proteins
How do overlapping genes and viral polyproteins work?
An overlapping gene is a gene whos nucleotide sequene overlaps with another gene, this does so the viruses has numerous ways to control the translation. It can make than more than one protein. A polyprotein is a single protein that can be cleaved into smaller proteins. It allows a virus to translate a large protein that is later cleaved into functional viral proteins
How can viral infections be treated
There are antiviral drugs and you can take a vaccin that is a preventive treatment.
Prion
Proteinaceous infectious particle and misfolded proteins that lacks both DNA and RNA
How do prions cause disease
They can casue neurological diseases by triggering normal proteins to misfold into abnormal shapes. It can be spread between indivinudals if you consume contaminated tissue