So in this video, we're going to continue to talk about ways that cells can regulate their biochemical reactions by introducing post-translational modifications. And so recall from our previous lesson videos that translation is the cellular process of building proteins by using the encoded messages of mRNA. And so the prefix "post" actually means "after." And so, like a post-game interview is an interview after the game, post-translational modifications are just protein covalent alterations that specifically control protein activity and take place after translation. And so post-translational modifications are sometimes abbreviated as just PTMs, and it turns out that there are many different types of post-translational modifications, several hundred for that matter, and so we're not going to be able to cover all of the different types of post-translational modifications in our course. But there are some more common types of post-translational modifications that we expect your professors might want you guys to know about. And these include methylation, acetylation, ubiquitination, and phosphorylation.
And so down below in our example, we're showing you guys just a small handful of some post-translational modifications. And so notice, towards the top of our image over here, what we have is this pink squiggly line, which represents our mRNA molecule. And this pink arrow going downwards right here represents the process of translation. And so translation is going to build our protein molecule, which is right here, using the encoded messages of mRNA, just like what we mentioned up above. And so, again, any covalent modification that occurs to this protein after the process of translation is referred to as a post-translational modification. And again, there are many different types of post-translational modification. So these are definitely not all of them here and we're only showing you a small handful. Nine of them, to be specific.
And so the first post-translational modification that we're showing you guys is hydroxylation. Hydroxylation is just the process of taking our pro-protein and covalently adding a hydroxyl group to it. So hydroxylation adds a hydroxyl group. Now if we take our protein and instead of adding a hydroxyl group, we add a methyl group like this one, CH3, that is referred to as the process of methylation, which is, pretty straightforward, just adding a simple methyl group. Now, if we take our protein and we add a lipid to it, it's referred to as lipidation, and lipids tend to have these large hydrocarbons like this one right here. Now, if we take our protein and covalently add an acetyl group, like this functional group right here, this is referred to as acetylation.
Moving on to our next post-translational modification, what we have are disulfide bonds which we have talked about before in our previous lesson videos. And so we know that disulfide bonds will form between the R groups of two cysteine amino acid residues linking, potentially linking two separate polypeptide chains. Now, the next post-translational modification that we have here is ubiquitination. And ubiquitination, we will talk about more as we move forward in our course, but really it's just this process of taking a protein and covalently adding a small protein to it, called ubiquitin. Now, the next post-translational modification is sulfonation, which is adding a sulfate group to the protein. And then we have glycosylation, which is adding a carbohydrate to our protein. And then last but not least, what we have up here is phosphorylation. Phosphorylation. And phosphorylation we will also talk more about later in our course, and it's simply the process of adding a phosphate group to our protein.
And so this here concludes our introduction to post-translational modifications. And, as we move forward in our course, we're going to continue to talk about very select types of post-translational modification. So, I'll see you guys in our next video.
