the next thing we want to do is understand how the information in DNA is actually turned into a protein that's going to do the work of the cell and in order to do that I want to break this up into a couple of pieces I want to talk about the components of translation the pieces that the cell needs to get that done and then we'll talk about process including another animation for you to review the first thing I want to talk about are the different kinds of RNA I have really focused just on messenger RNA so we've talked about the DNA being opened up RNA polymerase binding the promoter synthesizing a gene right that Mester RNA is going to come from a specific gene in the DNA and then detaching from the DNA the DNA rewinds and the messenger RNA goes out finds a ribosome there are actually two other kinds of RNA to get made by RNA polymerase and so one of those is ribosomal RNA and that's actually a structural component of the ribosome itself it's part of the ribosome it makes up the bulk of the structure as well as function has has enzymatic function in the ribosome the other RNA that is made is called transfer RNA and transfer RNA actually brings amino acids to the ribosome so that the ribosome can build proteins from those amino acids now if you look at a messenger RNA molecule it's divided up into something called codons and so we know that there are three bases that are required for each amino acid and we'll talk more about that in the next slide but for now each of these three bases is a codon and you can see that we have three codons so far that have been labeled here so here's the first one here's the second one here and here's the third one and so the first codon Aug that tells the ribosome that it needs to bring a Massiah knee that's the amino acid that's going to start this protein actually Matheny is always used at the beginning of protein so Aug is always the beginning of a protein that's something that si - no notice that what's bound to it is this transfer RNA molecule and it has a complimentary sequence that's called the anticodon the anticodon it binds to the codon in the messenger RNA and that's going to have a complimentary sequence so you AC is complimentary to a new gene and this transfer RNA with the anticodon UAC will always bring a Massiah mean to the ribosome the second codon in the messenger RNA is you you see it's complementary anticodon is a AG and a AG anticodon on a tRNA will always bring a phenylalanine to the ribosome to build proteins and then the third one that the labels here has a codon of a AAA and the messenger RNA and it binds exclusively to the anticodon uuu the transfer RNA with the anticodon uuu will always bring a lysine to the ribosome and as these are brought to the ribosome the ribosome actually forms the peptide bond between these amino acids and begins creating a protein and this is the primary structure from these amino acids one of the interesting stories is just how scientists figured out the genetic code they've called this the rosetta stone of biology because after Watson and Crick published their paper describing the structure of DNA it was pretty clear that the sequence of bases was informing the cell what order to put protein amino acids into proteins but at that point they didn't know what that code how to read that code and so they did some experiments some of them were thought experiments so for example we knew that there were 20 amino acids that were found in in proteins and if you had one amino acid per base that would only allow you to encode four amino acids so they were confident that it couldn't be just for it couldn't be a direct relationship you know adenine was one amino acid the time you know is another it had to be more complex than that if you if the if each amino acid was encoded by a two base sequence that would give you sixteen combinations for two the two is sixteen and that's not enough right twenty is more than sixteen so they figured it might be 3 because four to the third would give you 64 combinations and that would be certainly enough for 20 amino acids and the kinds of experiments they did was they would make synthetic messenger RNA was only used and they would find that you always got phenylalanine when you made only use and if you made only a's you've got lysine and then they would do little segments where they do you you a you you a you you a and they did experiments like that until they had cracked the whole code and they figured out exactly what the sequence was for every amino acid and some amino acids are encoded by more than one codon so for example phenylalanine is encoded by you you you and you you see and there are some with for probably and is actually encoded with all four of these sequences now how do you read a code like this well this is first position so the first but if you know that your codon starts with a u then that you would you would go to this particular row if your first position was an a you would read from this row the second position is here right and then the third position is along this particular row so for example if I wanted to find the amino acid that was encoded for CAC I would go down to C and then I would go down to a and then I go across to C and I find it right here and I noticed that it was his team okay so histidine actually is the I said that wrong its histidine so that's how you read the genetic code a couple of other things that are really important I said on the last slide that Aug always in codes in the thiamine and that's always the start codon so whenever you're looking for beginning in a protein you want to look for that first Aug because that's usually the beginning and then there are three sequences that don't encode any amino acids and these are our stop codons so UAA UAG and UGA or stop codons you do not need to memorize any of these because you can look them up on your phone if you ever needed it right it's not that critical if this was ever going to be on a test I would provide you with a genetic code but I would expect you to be able to read the genetic code so if I gave you a sequence and I said you know what amino acid is encoded by the codon GAA I would expect you to be able to go here and read it and tell me that it's atomic acid in this particular case at least give me the three-letter code that's there at the Glu okay so another interesting thing is is just the structure of transfer RNA I told you before when we talked about RNA structure that RNAs can base pair with themselves we call that intramolecular hydrogen bonding and so transfer RNAs are kind of a classic here is an example it's a single molecule of RNA but you can see a base pairs with itself here and here and here and it forms this really nice cloverleaf shape and at the base of the cloverleaf here is the anticodon and we said that matches up with a codon in mRNA if you wanted to look at this in a more molecular space-filling model method you'd kind of see it looks more like this with the amino acid attachment site which is shown here right here so the amino acid is hooked here or if you look at it kind of an A it looks like a question mark a little bit if you want to draw this without the space filling model so the anticodon is that one in essentially in the amino acids are attached at the other end of the transfer RNA there is a specific enzyme called an amino acyl tRNA synthase that charges transfer RNAs and what do we mean by charging well this particular enzyme is responsible for adding amino acids to the transfer RNAs and getting them ready for protein synthesis so here's the enzyme and what's gonna happen here is the first thing is this isn't free it's gonna cost the cell some energy okay so what we should see I hope maybe I'll have to set it to the slide again so it will go come on little animation okay I've gone back a slide and I think I figured out how to get this gift to play again it seems to do it one time and then stop instead of playing over and over again so I'm gonna go forward in the next slide and then we're going to go through this gift kind of quickly all right so what's happening with this enzyme is it's taking the amino acid which is valine and it's not going to be free so this is an ATP so it's gonna release two phosphates that's got energy it's added the phosphate to the valine here's our uncharged tRNA it's going to lose that high-energy bond and then now we have the amino acyl tRNA with a valine on it and it's ready to go and participate in protein synthesis so each time one of those transfer RNAs drops off an amino acid it's going to go back to the enzyme that charges it and get another amino acid and then it can go back and participate again in the process of protein synthesis but you can see how each time this happens it costs the cells of energy and ATP gets used up so when we talk about catabolism and anabolism in the cell we say you know anabolic pathways require energy generally speaking this is an example here we are building a protein and we're using in an ATP every for every amino acid that gets put on a transfer RNA so this is just a nice illustration of how cells need energy to do things right it's costing the cell energy in order to charge these tRNAs with their amino acids that they need to bring to the ribosome okay so the next thing I'm going to show you is an animated overview of translation and then I'm gonna go through the steps with you one by one as well