15. Gene Expression
Steps of Translation
1) Initiation of Translation
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in this video, we're going to begin our lesson on the steps of translation and so very similarly to transcription. The process of translation also consists of three steps and they are named the same as their named in transcription. So it starts with the initiation process and then it moves on into the elongation process. And then last but not least, it moves on to the termination process. And so as we move forward in our course, we're going to talk about each of these three steps of translation in their own separate videos, starting with the initiation process. And so, in the initiation of translation, of course, we know initiation just means the start or the beginning of the process. And during the initiation of translation, it turns out that the small Ribas almost sub unit of the rib zone is actually first going to bind to the messenger RNA and a T Arna before the large drivers almost sub unit even comes into play and binds. And so if we take a look at our image down below at the initiation of translation, noticed that at the very beginning the small ride is almost sub unit which we're showing you here is going to bind to the messenger RNA, the M r N a first and the messenger RNA uh, eyes, then going to associate with the t r n a that you see here. And so the small right is almost sub unit is going to bind to the messenger RNA and the t r n A. Before this large rivals almost sub unit. Over here, the large rivals almost sub unit even comes into play. And so that's really the sequence of events here. The small ride was almost sub unit binding to the Mara and then the tiara. And then lastly, here, the large drivers almost sub unit is the last component to come into play during initiation. Now, one thing to note is that, of course, the Amarna, the messenger RNA, is going to contain the co dons the three nucleotide sequences. And so the very first coat on is going to be the start. Code on is what's known as the start coat on, and the start coat on is going to be a you g a. U G is the start code on that specifies Thea amino acid meth une or M E T. And so the start code on a U. G that specifies the amino acid meth inning is going to initiate the start of translation during this initiation process. And so what you'll notice here is that here in the m r n A, we have the code on a U. G. And this is going to be the start code on. And, of course, the code on are going to specify amino acids through the T Arnas. The transfer RNAs, which are going to have antique Oden's that air complementary to the code on. And so the tiara, of course, is going to be a charged tr nay that is attached to an amino acid. And this amino acid this that corresponds with the start coat on is going to be Matthiasson in which is abbreviated as M e t. Until we can put em e t in here. And so that is going to be the first amino acid in the chain of the poly peptide chain. Now it turns out that the initiation of translation is actually can be quite a complex process. It actually involves several proteins that are called initiation factors, which were actually not showing you here in this image. Um, and translation. The initiation requires energy as well, which we are showing you the energy here. Uh, thio remind you that it does require energy. And so, ultimately, at the end of, uh, the initiation of translation, we have the complete intact ribs, um, bound to the messenger RNA and the very, very first tr in a that corresponds with start coat on on the amino acid. Matheny. And so this here concludes our introduction to the initiation of translation and the steps of translation. And we'll be able to talk Maura about these steps of translation as we move forward in our course, continuing with elongation. And then, of course, ending with termination. So I'll see you all in our next video.
2) Elongation of Translation
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in this video, we're going to talk about the second step of translation, which is the elongation of translation. And so, of course, E elongation just means making something longer. And what's going to be made longer is the growing poly peptide chain, the growing amino acid chain. And so, during the elongation of termination, amino acids are going to be added one by one to the previous amino acid at the C terminus of the growing chain. And so therefore, this means that the poly peptide chain is going to be growing from its in terminus to its C terminus. Now the ride zone again is going to be the main, uh, structure involved with translation, and it's going to be reading the Marna, the Messenger RNA and Cody Johns. It's going to be reading the Marna code ions from the five prime end of the Marna to the three prime end of the Marna. And as it reads these katanas, these three nucleotide sequence the rhizome is going to be pairing each of the Karnak Oden's with the correct respective Trn a antique Oden's and those tr Anna's we know are going to be specifying one amino acid And so each code on will specify one amino acid by pairing with a TR in A that is attached to that amino acids. Now, the way that translation elongation works is that new T Arnas that air charged and attached to amino acids are going to enter the ribosomes a site and then shift into the ribosomes p site. And then finally, they're going to exit the ride his own through the ribosomes e site before exiting. And so if we take a look at our image down below at the elongation of translation, we can better understand how this process works. And so here, at the very beginning, what we're showing you is the end result of the initiation of translation where we have the small and large rivals, almost sub unit are intact and bound to the very first t r n a on the messenger RNA, the Marna. And so what you can see here is that charged T Arnas or TR names that are attached to amino acids are going to enter into the ribs, um, into the ribosomes a site. So that's what we have here as the very first step here that charged tr nas air going to enter into the ribs own via the A site on. Then what's going to happen is a peptide barred is going to be formed and recall that a peptide bond is a covalin bond between amino acids. And so what happens here is that the first amino acids, uh, in this position is going to be co violently linked to the next amino acid. And so it gets passed on to this, uh, Trn a here. And so you can see they've been co violently linked these two amino acids. So we have a growing amino acid chain here. Now what happens is the rhizome is going to continue to shift along the Marne A and that causes the discharge. Tierno, remember, discharged RNAs or Tierney's that air not attached to amino acids because again, it's amino acid was, uh, linked to the previous amino acid. And so the discharge DNA is going to, uh, enter and exit, uh, enter the, uh, the east site and, uh, exit into exit the ribs own through the east site on. So you can see here that the discharge tiara is exiting through the east site. And meanwhile the other tiara is shifting into the P site. So the tiara is going to shift into the peace site on. Ultimately, the process is going to repeat. So we have a growing amino acid change. So now a new tr nay could enter into this position. A new peptide bond would be formed between that amino acid. And then again, the process would just continuously repeat over and over and over again to continuously add amino acids and grow this poly peptide chain. And so that is going to be the elongation of translation. And we'll be able to talk about the final step of translation the termination of translation in our next video, so I'll see you all there.
3) Termination of Translation
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in this video, we're going to talk about the third and final step of translation, which is the termination of translation. And so, of course, termination means to put something to an end. And so during termination, the process of translation will be coming to an end. And so, during the termination of translation, a stop code on is going to reach the ribosomes, a site, and that is going to trigger a release factor protein to bind. And so if we take a look at our image down below, we can see that we have our growing poly peptide chain here and here. What we have is the next coat on. But this code on notice is a stop code on U G. At. And so the stop code on is not going to be associated with a Trn A. Instead, the stop code on is going to trigger a release factor protein this orange protein to bind. And so when the release factor protein is bound, it's going to trigger a Siris of events. First, the poly peptide chain is going to be cleaved and released from the T r n A. And so you can see that the tiara over here is no longer bound to the poly peptide chain over here as it was over here in this side. And so what we end up getting is our final poly peptide chain is right here at this position that is going to be released. And also the entire translation assembly is going to come apart as well. Uh, due to this release factor, and so the release factor gets the release, The Mara is released, the small and large rival zonal complex are going to disassociate from each other. And again, uh, the final protein chain poly peptide chain is also released. And so that terminates the entire process of translation. And so this year concludes our breathe lesson on the termination of translation and we'll be able to get some practice applying the concepts that we've talked about here and the steps of translation as we move forward in our course. So I'll see you all in our next video
Which of the following processes is the first event to take place in translation?
Base pairing of charged methionine-tRNA to AUG of the messenger RNA.
Binding of the larger ribosomal subunit to smaller ribosomal subunits.
The ribosome reaches a stop codon.
The small subunit of the ribosome recognizes and attaches to the mRNA.
Which of the following does not occur during translation's termination step?
The first tRNA brings the amino acid methionine to the ribosome.
The small and large ribosomal subunits separate from each other.
The polypeptide is released from the ribosome.
A "stop" codon is reached by the ribosome along the mRNA.
What is the function of the release factor during translation?
It binds to the stop codon in the A site in place of a tRNA.
It releases the amino acid from its tRNA to allow the amino acid to be added to the growing polypeptide.
It supplies a source of energy for termination of translation and the release of the polypeptide.
It releases the ribosome from the rough endoplasmic reticulum and allows the polypeptide to enter the cytosol.
Additional resources for Steps of Translation