Translation

Hi in this video we're gonna be talking about RNA translation. So first we're gonna go just a brief overview of translation. A lot of this is probably going to be familiar but I might be introducing a few new concepts before we get into really the nitty gritty details of how translation happens. So the first thing is translation is the process of changing an M. RNA transcript to a protein. And the main driver of this is the river zone. So it really drives translation. And we've talked about this before consists of two subunits small and large which is made up a combination of RNA and protein. And RNA actually makes up the majority of the river zone where we'll be around two thirds of the ribosome and is responsible for a lot of its enzymatic properties. So the river zone is affects sort of translation because it binds to T. R. N. S. In three different locations. Remember T. RNA sort of adapt between the R. N. A. And the river zone because they actually are the ones that carry the amino acids that form the protein. Now these three locations are called the A. P. E. Insight and they all have fancy little names here but generally just need to know ap or ap. And the A site is where the Trn A recognizes the code on the P site is where the amino acid is actually linked to the polyp peptide chain and the east side is the exit side. So it leaves it exits the ribosome now in order to initiate there's a special initiator tr nay that initiates translation. And this is bound to both the start code on. But also on the amino acid. A really special Athenian which acts as the initiator amino acid to start protein synthesis. So um in pro carry oats this is bound to this really special method meaning called informal method meaning but again we don't really focus a lot on pro carry oats but I do want to mention it here just because there are some differences. And this card on here is A G. So if we're to look at what this looks like me back out here title is overview of ribosomes sites and M. RNA translation. But you can see here that there is an A site A P site and there's also an east side of it a bit exiting here E. Really of exiting. And so what happens is you have your T. RNA bound to amino acids and it comes in and in the A side it recognizes the um nucleotides. In the P. Side it adds a amino acid to the polyp peptide chain and in the east side it exits. So that's kind of the overview of translation. Um Let's now turn the page

Okay so you will notice that this is another video about steps there are a lot of steps in cell biology and so we're just gonna have to get through them. So let me disappear. Um It's really complicated but I'm going to walk it through. Walk this through slowly I'm gonna disappear so we make sure you can see everything and I'm not standing in the way. So the very first step to translation is that the T. RNA binds to the small subunit of the ribosome and other translation initiation factors. So it's not just the rib is. Um There are all these other proteins which you'll see in your textbook called I. S. And E. I. S. Um And these translation initiation factors are also important for translation. And so it's important here to know that this first trn A site binds the P. Site. Do you remember is kind of the second site. Um And only the initiator T. RNA combined here. Um And only when the large subunit isn't attached. So this very first step is a really unique thing where the the initiator TRN A binds to the P. Site which is kind of weird and that only happens before you know it interacts with any kind of R. N. A. Um or even the large sub unit. And so once the initiator um T. RNA. Is bound to the small subunit of the ribosome it can bind the five prime end of the M. RNA transcript. Where it then scans till it reaches A. G. So if we're going to look at this, what we're going to see is you're going to have your small sub unit and your initiator T. E. R. N. A. And this is your method meaning amino acid And they bind together. So this is really step one. And here's some other factors here. The Z. I. S. I. S. Here's another one. E. I. F. Four. Now step two is they're recruited to this five prime end and then they move along here until they find the start sequence. Which if you can see that is actually a U. G. So this is the start code on for translation. Now when it gets to the A. U. G. Site, what happens is it stops and the large subunit is recruited to the site. And so you can see here um and then all of these different factors uh leave. So you can see here that it stopped here on this au AU G site. This large subunit comes in um binds forms this rivasseau more complex and all the other factors leave go somewhere else. So now we're on step four. What happens at step four is um it starts going through the different sites. So the amino acid is cleaned from the initiator R. N. A. Which is in the P site. And so that forms the very first amino acid and then this more T. RNA is continually to be brought to the A site. And so you can see this here this image you have your initiator. Trn A. the large sub units coming in being recruited and eventually this amino acid goes up to start forming the peptide change where other TR N. A. S. Are continually brought in. So this is repeated over and over again. You're about to see to form the whole polyp peptide chain. But it's important to realize that there's a large subunit and a small subunit of the river zone and each of them have different functions. So the large sub unit is actually responsible for binding the amino acids together and the small subunit is responsible for matching T. R. N. A. S. Two M. RNA code ins So that's just sort of you know which sub unit is doing what now? Um As these uh let me scroll down here as these amino acids continually linked together. You see you get forming these uh polyp peptide chains. And so um once the amino acid is added the river zone moves three nucleotides one coat on each time, and the T. RNA moves down the site. So you can see here, it starts here. It enters here, he said yeah enters here. Oh you can't see that because it's green. It enters here. See any of these enters here at the a site and then it moves to the p site. Remember the a site it recognizes the code on and the p site it adds amino acids. And so every time it's added another T. RNA comes in and it's all replaced and one exits. And it's all moving three nucleotides at a time sort of the ribosomes chugging along three nucleotides at a time. And so um there you know of course other proteins called elongation factors that come in and assist in this translation elongation. Um it can require energy using GDP hydraulic sis. One that you might read about in your textbook often is called E. F. Two. And this uh really helps T. RNA. Is to bind M. RNA and pro carry oats. And so these are just doctors that really helped the ribosomes keep chugging, keep matching T. RNA and protons. But eventually the Trn A exits the rib a zone. Um And the process continues continually. 5 to 3 prime until it reaches the end. Now for termination um translation is terminated here when it reaches the stop code on here are the three ones here. And when it reaches here, what happens is there are these things called release factors that come they hide relies or break apart the water molecule and that releases the protein and the ribbon zone from the M. RNA. And that can be started again. So what you see in this image you finally reached a stock coat on here. It is it reaches a release factor comes in that breaks apart water. And when that breaks apart it releases energy and releases the ribosomes off of the M. RNA. And this concert again. So these steps are really long. Really complicated involve a lot of factors feel free to watch this video as many times as you need to kind of get down. You know what the steps are and how they work and anything you might be confused about. Um But overall these steps occur really quick quickly and they can require lots of ribosomes. Um So mammals have 10 million ribosomes, 25% of the coli weight is just from ribosomes, so translation is really important. It's really complicated and it occurs really quickly. So now let's move on.

Okay in this video we're gonna be talking about pro carry optic translation. So translation and pro carry optics cells is different because in eukaryotic cells the ribosomes depends on having a five prime cap on the transcript. But pro carry oats don't have that. So they have to have a different way for the rift zone to find. So how does this is through the shined algoma sequence? And this is where the pro carry attic ribosomes bind. And so just the thing to know other than the Shine Delgado mo sequences that the pro carry optic ribosomes slightly smaller than the eukaryotic ribosomes. And antibiotics generally work by targeting pro carry on ribosomes. But while leaving the eukaryotic ribosomes alone. So if we're just going to look at a brief sequence here, here's an M. RNA sequence. Um and of a pro cario and here you have your shine down gamma sequence. Go on those sequence and the ribosomes comes in binds here and then can translate this RNA into protein in pro cryonics house. So like I said, this is going to be short but just a general overview of pro periodic translation. So let's move on

Hi in this video we're gonna talk about polly ribosomes. So what are poly ribosomes? They are just a bunch of ribosomes that accumulate on a single transcript so that multiple RNA copies can be translated at the same time. So it's really efficient. It saves time. And each rib zone where the next zone can begin when the preceding one has translated about 8 80 nucleotides. So if we're just going to look at what this looks like, we can see here that we have our M. RNA transcript, We have our little boxed ribosomes that look like this and about every 80 nucleotides a new one jumps on. So these little blue circles here Amino acids and you can see that you know further down the transcript there's more chains. But before this is finished more ribosomes keep jumping on and they form these poly ribosomes that can be translating the same transcript multiple times. Um And this saves a lot of time and it's really efficient. So I said this will be brief. It was this is polly river zone. So let's move on.