In this video, we're going to begin our introduction to translation. And so recall from our previous lesson videos that translation is the process that builds proteins by using the encoded messages of mRNA or messenger RNA. Now in the process of translation, these structures, called ribosomes and transfer RNAs or tRNAs, are going to be very important. And so ribosomes are going to be very complex structures made of proteins and ribosomal RNA or rRNA. And these ribosomes, these complex structures, they're going to be the main structure that's important for building proteins once again, and therefore, it's the main structure that's important for performing translation. Now throughout the process of translation, building the protein, these ribosomes rely on these transfer RNAs or these tRNAs for short. And so the transfer RNAs are going to be RNA structures themselves, but they are not going to be translated into a protein. Instead, the transfer or tRNAs are going to be important for carrying or transferring amino acids to the ribosomes during translation. And so they're pretty much bringing amino acids to the ribosomes. Now the tRNAs are going to contain anticodons. And so the anticodons are going to pair with the mRNA codons during translation. And so this pairing of the anticodons with the codons is what's going to specify one amino acid that's associated with the tRNA anticodon with one mRNA codon. And so we'll be able to talk more details about this process as we move forward through our course. Now one thing to note about these tRNA's is that they can really come in 2 states, one of 2 states. The first state is the charged state, the charged tRNA. Now the charge here, this term charge has nothing to do with the electrical charge. And so the tRNAs do not actually have an electrical charge. Instead, this term charge is referring to something different other than a positive or negative electrical charge. Charged tRNAs are tRNAs that are attached to an amino acid, and that is really it. Has nothing to do with electrical charge positive or negative. So charged tRNAs are the attached tRNAs that are actually attached to an amino acid. Now discharged tRNAs, on the other hand, again, has nothing to do with the electrical charge, positive or negative. Instead, discharged tRNAs are the opposite of charged tRNAs. Charged tRNAs are attached to an amino acid. Discharged tRNAs are not attached to an amino acid. And so we'll be able to see this down below in our image. Now in our example image down below, we're showing you the different variations of transfer RNAs or tRNAs during translation over here. Over here on this side, what we're showing you is just the process of translation. Taking the encoded messages of RNA, and translation is the process of using those encoded messages of RNA to build a protein. And of course, the process of translation relies heavily on the ribosome, which is going to be the main structure responsible for translation. And of course, the tRNAs, And the tRNAs are going to be important for bringing amino acids to the ribosome. And again, we'll talk more and more about the details introduction. And so, taking a look at the tRNA over here, what you'll notice about the tRNA, the transfer RNA, is that it is a long RNA molecule, and it is going to be attached to an amino acid. And when it is attached to an amino acid, it is referred to as a charged tRNA. And so the amino acid in this image is being represented by this blue circle, so that would be the amino acid. Now the discharge tRNA is not going to be attached to an amino acid. You can see the amino acid attachment site is here, but there is no amino acid here. And so because there's no amino acid here, it makes this over here a discharge tRNA, not attached to an amino acid. Now again, the tRNAs themselves are going to have anticodons, 3 nucleotide sequences that pair with the codons on the mRNA. And so here what we have is the anticodon on the tRNA. And notice that the anticodon on the tRNA is pairing translation, and that is what is going to help translation, and that is what is going to help specify the process of translation. And, again, we'll talk more details, all of these details, and reveal them, as we move forward through our course. But one thing to keep in mind here is that, once again, translation is going to build proteins using the encoded messages of mRNA. It is going to rely heavily on ribosomes and transfer RNAs or tRNAs. And so we'll talk more about translation as we move forward in our course, so I'll see you all in our next video.
Introduction to Translation - Online Tutor, Practice Problems & Exam Prep
Translation is the process of protein synthesis using mRNA, facilitated by ribosomes and transfer RNAs (tRNAs). Ribosomes consist of two subunits: the small (30S in prokaryotes, 40S in eukaryotes) and large (50S in prokaryotes, 60S in eukaryotes). tRNAs carry amino acids to the ribosome, entering through the aminoacyl (A) site, transferring to the peptidyl (P) site, and exiting from the exit (E) site. Charged tRNAs are attached to amino acids, while discharged tRNAs are not. Understanding these components is crucial for grasping the translation process.
Introduction to Translation
Video transcript
What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?
The tRNA shown in the figure has its 3′ end projecting beyond its 5′ end. Which of the following processes will occur at this 3′ end?
Ribosome Subunits
Video transcript
In this video, we're going to talk more about ribosomes, specifically the ribosome subunits. Ribosomes, as you may recall, are the main structures responsible for translation and consist of two subunits, referred to as the small and large ribosomal subunits. Each of these subunits, the small and large ribosomal subunits, are made of proteins and ribosomal RNA or rRNA. It turns out that the ribosomes of prokaryotes differ from the ribosomes of eukaryotes. Notice in our image below; we will be talking about prokaryotic ribosomes on the left-hand side, and on the right-hand side, we will focus on eukaryotic ribosomes. It's very important to distinguish the complete intact ribosome from the ribosomal subunits that come together. You will notice there is a large ribosomal subunit and a small ribosomal subunit. The large and small ribosomal subunits need to come together to form the complete intact ribosome.
Prokaryotes have a complete intact ribosome with both subunits combined, referred to as a 70S ribosome. The complete intact ribosome for prokaryotes with both subunits combined is called a 70S ribosome. The 70S ribosome of prokaryotes is made of these two subunits, the large ribosomal subunit and the small ribosomal subunit. The large ribosomal subunit on its own, when it is separate from the small ribosomal subunit, is referred to as a 50S large ribosomal subunit. The small ribosomal subunit of prokaryotes is referred to on its own as a 30S small ribosomal subunit. One thing to note here is that 50+30≠70. That's okay. This is not going to be the sum of these two subunits that gives you the complete intact ribosome. This "S" here is a Svedberg unit, which describes how these ribosomes would sediment or centrifuge in a complex process.
Eukaryotes, on the other hand, have an 80S intact ribosome. The complete intact 80S ribosome in eukaryotes is made up of smaller components, the smaller subunits, the large subunit, and the small subunit. The large ribosomal subunit in eukaryotes is a 60S large ribosomal subunit and the small ribosomal subunit for eukaryotes is a 40S small ribosomal subunit. Once again, 60+40≠80, but that's okay. That's how this process works. The 80S ribosome is composed of the 60S and 40S subunit.
How are you supposed to remember this process and the details of the prokaryotic and eukaryotic ribosomes? An easy way to remember is to notice that all of these numbers are basically just going 30, 40, 50, 60, 70, 80. So I write down all the numbers in their order, and then I put them in pairs: 30, 40; 50, 60; 70, 80. The 30, 40 represents the small ribosomal subunits, 50, 60 the large ribosomal subunits, and 70, 80 the complete intact ribosomes. The smaller number within each pair is prokaryotic, so the 30S is here, the 50S is here, and the 70S is here. The larger number in each pair is eukaryotic, so the 40S is here, the 60S is here, and the 80S is here. By ordering these numbers 30, 40, 50, 60, 70, 80, and doing what we talked about here in this video, you'll have no problem remembering the components and the differences between prokaryotic and eukaryotic ribosomes.
This concludes our brief introduction to the ribosomal subunits, and we will continue to talk more about ribosomes and the process of translation as we move forward in our course. I'll see you all in our next video.
Ribosomal tRNA Binding Sites
Video transcript
In this video, we're going to talk more details about the ribosome, specifically the ribosomal tRNA binding sites. And we'll talk about an overview of translation as well. Now keep in mind that this video is really just going to be the introduction and the overview of the ribosomal tRNA binding sites and this process of translation. But as we move forward in our course, we're going to break down the process of translation into its steps. And so we're going to talk more details about translation as we move forward in our course, and this video here is really just the overview. So keep that in mind as we move forward through this video. And so each of the ribosomes is going to have 3 tRNA binding sites. And so recall that the tRNAs are the transfer RNAs that are going to be attached to amino acids and bring amino acids to the ribosome. And so, the tRNA binding sites are going to be found within the ribosome, and there are 3 tRNA binding sites. The first tRNA binding site is going to be the aminoacyl tRNA binding site, otherwise just abbreviated as the A site. And so the A site is going to be the site where the tRNAs are going to originally enter into the ribosome. And so it holds the tRNA that's carrying the next amino acid to be added. And again, tRNAs will enter into the ribosome through the A site. And so if we take a look at our image down below, what you'll notice is we've got our ribosome, our complete intact. And so this right here represents our mRNA, our messenger RNA. And so what this ribosome does is it will receive tRNAs like this one right here. This, box here represents the tRNA. And because it's attached to an amino acid, this little purple circle here represents an amino acid. That makes this tRNA a charged tRNA. And again, the charge has nothing to do with the positive or negative electrical charge. Instead, the charged tRNAs are attached to amino acids. And amino, tRNAs, charged tRNAs are originally going to enter into the ribosome into the A site. So you can see the first site here is the A site. Now the second ribosomal tRNA binding site is going to be the P site or the peptidyl tRNA binding site, otherwise known as the P site. Now the P site is going to be the site that is going to be holding the tRNA that's carrying the growing polypeptide chain or the growing protein chain. And so if we take a look at our image down below, what you'll notice is the P site is here in the middle, and the P site is going to be holding the tRNA that is attached to this growing polypeptide chain here. So, this background right here, it represents the growing polypeptide chain. And so, the P site is going to have the amino the tRNA, that is bound to the growing polypeptide chain. And so notice that the tRNA is going to have the anticodon, and the anticodon is going to pair with the codon of the mRNA. And so this will be a process that we'll talk more details about as we move forward in our course. Now the third and final site of the ribosomal tRNA binding site is going to be the E site or the exit site. And so the E site, or the exit site, of course, is going to be where the discharged tRNAs are going to leave the ribosome from this site. And so the E site is going to be on this end of the ribosome, and the E site is the exit site. And so the discharged tRNAs, which again has nothing to do with the electrical charge positive or negative, instead discharged tRNAs are not attached to an amino acid and that's because the amino acid was transferred over to this growing chain here, this growing polypeptide chain. And so the discharged tRNA is without the amino acid are going to exit the ribosome through the E site. And so what we're seeing here is that charged tRNAs are bringing amino acids to the ribosome and they're entering into the A site. Then the P site is going to be, contain the growing polypeptide chain where the amino acid is just going to be added to the growing polypeptide chain. And then, the ribosome is just going to continue to shift along the mRNA and, what happens is that the, tRNAs in the P site will shift into the E site and then eventually exit the ribosome in this way. So basically what's happening is charged tRNAs come in, they make their way from the A site to the P site to the E site and then ultimately leave the ribosome. And, again, this is a very detailed and complex process that involves a lot of moving pieces. And so this here is really just the introduction to these three ribosomal tRNA binding sites, and we're going to talk more details in a step-by-step manner, of the process of translation involving all of this as we move forward in our course. But for now, this here concludes our overview of the tRNA binding sites, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
A ribosome has three tRNA binding sites. Which answer matches the tRNA binding site with the correct function:
Which of the following statements concerning ribosomes are true?
The direction of ribosome movement during translation is in the ______________.
Many antibiotics work by blocking the function of ribosomes. Therefore, these antibiotics will:
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