Animal Viruses: 1. Attachment to the Host Cell

in this video, we're going to continue to talk about animal viruses and animal virus infections by talking about the very first step in an animal virus infection which is attachment to the host cell. And so first we need to recall from our previous lesson videos that the very first step in a bacterial fage infection was also attachment to the host cell. And so it turns out that animal virus attachment to the host cell is actually really similar to bacteria fage attachment to the host cell. And so it turns out that it relies on protein interactions. And with animal virus. In fact attachment, it involves spike proteins. And so spike proteins on the surface of the animal virus are going to recognize and bind to vary specific host cell receptors. And this binding and attachment that the spike proteins on the virus make with host cell receptors is really what allows for the virus to enter uh into the host cell. An entry into the host cell is going to be the second step. And so if we take a look at our image down below, we can get a better understanding of this very first step of an animal virus infection which is attachment. And again with this very first step of attachment. This is when the animal viruses going to attach to the surface of the host cell. And so more specifically, it's the spike proteins on the virus that are going to bind to host cell receptors. And so what you'll notice is on the left hand side of our image over here, what we're showing you is a non enveloped virus or a virus that does not have an outer lipid layer. And so this non enveloped virus which will notice is that the spike proteins are right on the coat of this virus and the spike proteins will interact with receptor proteins on the host cell and when it binds that is the attachment stage. Now on the right over here, we're showing you an enveloped animal virus and the enveloped animal virus has an outer lipid layer and outer lipid envelope that surrounds the protein coat and notice that the spike proteins are going to be protruding through to the outside of this envelope. This lipid envelope. And once again it's the spike proteins that will interact with surface receptors, the host cell receptors here. And that interaction is what allows for attachment and attachment is necessary for entry, which is the second step of an animal virus infection. And so this here concludes our lesson on the very first step of an animal virus infection, attachment to the host cell. And we'll be able to get some practice and continue to learn more about animal virus infections as we move forward in our course. So I'll see you all in our next video