Animal Viruses: 5. Release from Host Cell - Video Tutorials & Practice Problems
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concept
Release of Enveloped Viruses
Video duration:
5m
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in this video, we're going to continue to talk about animal viruses and animal virus infections. By specifically focusing on the fifth and final step of an animal virus infection, which is release of the new viruses from the host cell. Now, it turns out that this fifth step is actually a little bit different and enveloped viruses and non enveloped viruses. And so in this video we're going to focus on the release of enveloped viruses. And then later in a different video, we'll talk about the release of non enveloped viruses. And so once again, recall from our previous lesson videos that enveloped viruses are going to have an outer lipid envelope surrounding their new clio caps it. And so it's important to note that most enveloped viruses are going to be released from the host. So by a process that's known as budding. And so budding is the process that allows for the release of enveloped viruses by using the cell cytoplasmic membrane to actually form the envelope itself. And so, as we'll see down below in our image, the lipid envelope of an envelope viruses is actually derived from the host cell cytoplasmic membrane. Now, budding does not immediately kill the cell, the host cell. And so that is also important to note. And so if we take a look at our example image down below, we can get a better understanding of the release of an envelope animal virus from a host cell. And so in this image, we're going to start over here on the far left and we're gonna make our way from left to right in that direction. So, starting over here on the far left, notice that we're showing you a new clio caps, it of a virus that has assembled in the host cell cytoplasm. And so in order for this uh enveloped virus to eventually exit from the host cell. What needs to happen is the viral spike proteins are actually going to insert themselves into the cells cytoplasmic membrane. And so you can see here these little yellow structures that you see are the spike proteins that are actually going to insert themselves into the cell cytoplasmic membrane. And then what's going to happen is uh the matrix proteins are going to begin to bind and the viral envelope itself is going to begin to coat the Varian or the viral particle via those matrix proteins. And so recall that the matrix proteins which are shown here in pink are the proteins that link the nuclear capsule to the viral envelope that is forming here. And notice that the viral envelope is forming from the cell cytoplasmic membrane and budding of the cell cytoplasmic membrane. Now over here in this third image that you see, you can see that the nuclear caps, it is going to be fully coated with the matrix protein. And so notice that there is a matrix protein all the way around here and notice that the viral envelope which has viral spike proteins are also going to be surrounding the nuclear capsules. And so you can see the viral envelope with the viral spike proteins in here as well. And so ultimately what happens is the Varian or the viral particle is going to be completely released from the host cell. And so you can see here we have the release of the variant or release of the viral particle and it has its nuclear capsule along with its lipid envelope. And so it is a fully mature and a fully infectious virus virus. Now it is also important to note that occasionally some viruses, some enveloped viruses can actually obtain their lipid envelope from cells organelles. And so the envelopes can sometimes develop from a cell's organelles. Like for example, it could develop from the Golgi apparatus membrane or it could develop from the rough end a plasmid particular membrane rather than the cytoplasmic membrane. And so the way that that would work is the viral particle, the nuclear caps. It would bud into either the Golgi apparatus or the rough er and then through vesicles it would be released into uh the environment. But either way uh the enveloped viruses are going to be obtaining their lipid envelope upon being released from the cell. And so this year concludes our brief lesson on the release of enveloped viruses from the host cell and we'll be able to get some practice applying these concepts and then we'll talk about the release of non enveloped viruses from the host cell. So I'll see you all in our next video.
2
concept
Release of Non-Enveloped Viruses
Video duration:
2m
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in this video, we're going to briefly talk about the release of non enveloped viruses from the host cell. And so recall that non enveloped viruses do not have an outer lipid envelope and they are going to be released from the host cell after the host cell has died by triggering a process known as apoptosis. And so a apoptosis is really just a complex mechanism of programmed cell death that can be initiated by the host cell as the host cell is carrying out an immune response against the infecting virus. And so once the virus has been released from the host cell, the viral particles of course, can then go on to infect other nearby healthy cells that are close by restarting the entire infection process, starting with attachment, then shifting into entry and assembly, then synthesis and replication assembly and then finally ending off with release. And so down below in this image we're showing you an image of the release of non enveloped viruses from the host cell. And so notice over here on the far left, we're showing you these non enveloped viruses. And again, these non enveloped viruses are going to assemble on the inside of the cell and the cell cytoplasm. And so unlike enveloped viruses, which will be uh released uh and acquire an envelope through the cell cytoplasmic membrane or another one of the host cell's membranes uh here with non enveloped viruses, uh the host cell is going to undergo changes in shape and it changes in shape during the early stages of the process of apoptosis. And so you can see the cell changes in shape right here, and ultimately, uh, apoptosis, the process of programmed cell death is going to occur, and when the cell is programmed to die, the viral particles are able to escape and be released into the environment. And so once again, the released viruses can go on to initiate a new infection in another neighboring silk. And so this here concludes our brief lesson on the release of non enveloped viruses from the host cell, and we'll be able to get some practice applying these concepts as we move forward in our course. And so I'll see you all in our next video.
3
Problem
Problem
Which of these answers is a major difference between the release of enveloped viruses and the release of non-enveloped viruses?
A
Enveloped viruses assemble after release while non-enveloped viruses assemble before release.
B
Enveloped viruses when released cause the host cell to burst while non-enveloped viruses do not.
C
Enveloped viruses do not kill the host cell upon release, while non-enveloped viruses trigger host cell apoptosis.
D
All of the above answers are major differences between the release of enveloped and non-enveloped viruses.
4
Problem
Problem
All of the following descriptions of viral multiplication and viral nucleic acids are true except which of these answers?
A
Viruses replicate only in living cells.
B
Viruses contain DNA or RNA, not both.
C
Viruses use the cell's biosynthetic machinery to synthesize copies of themselves.
D
The nucleic acid of a virus is surrounding by a protein coat.
E
Viral mRNA, viral tRNA, and viral ribosomes are used in viral replication.
5
Problem
Problem
All viruses must be able to do which of the following?
1. Kill the host cell. 2. Inject their viral genome into the host cell. 3. Lyse the host cell. 4. Have their viral genome replicated by the host cell. 5. Be able to reproduce in the absence of living cells.
