although translation is the last step of the central dogma which involves DNA turning into RNA turning into protein there are additional modifications that can occur and these are called post transational modifications of those proteins and these modifications can add additional variation and diversity to the types of proteins your body can produce and this has been termed the proteome just like we have a genome which represents all of the genes that can be expressed by an organism the proteome is all of the proteins that can be expressed and the really interesting thing is even though our genome is incredibly expansive and has thousands and thousands of different genes the proteome is actually greater and the reason for this is that you can have variable splicing of different mRNA transcripts and that can influence the different proteins you can produce but also when you produce these proteins there are ways to control their expression and function by providing additional modifications to these proteins and thus the number of proteins that the human body is capable of producing greatly outnumbers the number of genes that we have and these modifications which we'll get into in more detail in a moment can involve things like methylation adding methyl groups acetalation adding acetyl groups ubiquitination which is important in the degradation of proteins and many other different modifications you can make which can change the way that these proteins fold it can change their stability where they localize sending them to different cell compartments as well as modifying their function activating and inactivating them and so forth and so just because you've completed the translation step and got into the protein doesn't mean that your ability to control and Vary the expression of these genes is over and so we'll get into several of the modifications that can occur after translation that can influence the physiology of an organism here we have a list of some of the different post transational modifications that you can make to proteins this list isn't intended to be exhaustive and it's not something that you'll be responsible for on your test but rather it's to demonstrate all of the different modifications that you can make to proteins in order to regulate their function and their processing perhaps their localization within a cell and many other factors that can relate to their overall function as a protein so some of them are methylation which is just adding a methyl group this is accomplished by methyl transferases and these remember that you're adding a hydrocarbon containing Group which is very hydrophobic so it can make the protein more hydrophobic and that can influence its folding because hydrophobic groups like to face inward they they don't like to be facing the cytool which is aquous and polar another thing that methyl is very relevant for is that there are some epigenetic modifications that can relate to methylation of the proteins as well as things that can involve methylation of genes an acetylation is basically adding an acetal Group which is this Ketone containing group to the N Terminus of that protein and it turns out that around 90% of human proteins can undergo this acetylation and that can influence function as well glycosilation glyco should tell you that that's sugars you can add sugars to it by adding a mono or polysaccharide group and these can have a lot of effects they can change the folding of the protein where they're distributed within the cell they can be signals to send the protein to one area or another it can influence the conformation or shape uh the stability of a protein as well as regulate its activity to a certain degree lipidation adding some sort of lipid group and the reason for doing this is because you want to send that to a more lipid friendly area for example some membranebound organel where you want that protein to go so something like the endoplasmic reticulum GGI apparatus the mitochondria directly to the membrane or to an endosome or lome to Aid with processing of that protein and again remember you don't have to memorize this whole list as much as understand the big picture if you add lipids to A protein that will make it more comfortable in an environment where lipids are found which is usually involved in the membrane or some organel that is membrane bound ubiquitination is something that targets a protein often times a misfolded protein for degradation and ubiquitin again another thing you don't need to know but which might help is that it's an amino acid that is encoded by 76 base pairs phosphorilation that's something you encounter a lot with kinases and phosphor lases and can greatly regulate the activity of different proteins that are involved in the cell cycle cell signaling cell growth and apoptosis which is programmed cell death phosphate groups are something you see in a lot of different places and so be aware that this the post- transational modification of proteins is another place where those phosphate groups can be useful in regulating function of different components and also you can have proteins that are cleaved by proteases some examples might be things like pepsinogen which is cleaved into pepsin and that allows it to then be a functional digestive enzyme but these can help activate process or specialize the various proteins to have a greater degree of regulation of their function and so the key with this is realizing how the modifications to these proteins influence the diversity of things that can be expressed from our genetic code you can have alternative or variable splicing sites which can influence the transcript and then beyond that you can have the proteins be modified post translationally after the translation process and once again you can control and regulate the function of different proteins within the body