Write a paragraph describing the abbreviated chemical reactions that summarize RNA polymerase-directed transcription.

Video transcript

Hi, everybody. Welcome back. Let's look at our next question in RNA polymerase directed transcription during elongation as particle residues asp along with magnesium MG, two plus ions coordinate the phosphates of the Roman nucleotides. The overall reaction is NMP, the N plus an NTP becomes an M P to the N plus one plus P P I an inorganic pyro phosphate, which of the following is correct about the 1st and 2nd magnesium ions. So I'm just going to post a quick diagram of what's going on here um in terms of the chemical reactions. So we can refer to that. So in the circles here, we have our two magnesium ions that are bound to those asked residues. And on the left here, we have our existing chain. Here's the five prime end of our um RNA chain that's being lengthened in that elongation process. And we're focusing here on the last base at the three prime end where the new nucleotide is going to be added. And then here is our NTP that's going to be added here. Um So we see that the first magnetism here binds to this alpha phosphate group on our base to be added. That stabilization there, that binding allows a nuclear attack on the part of this three prime O H that will form that phosphate ester bond adding on that new base. So there's the role of the first magnesium. The second magnesium we see here binds to the next two phosphate groups on the base to be added. So it's going to carry away that inorganic pyro phosphate with it as the new base is added. So with that in mind, let's look at our answer choices. Choice. A says the first magnesium ion binds with the pyro phosphate of NDP. Whereas the second magnesium binds with the alpha phosphate of NTP. Well, this is not gonna be our answer choice because this is reversed. It's the second might need to mind the binds of the pyro phosphate. While the first bonds with the alpha phosphate choice pieces, the first magnesium iron bonds with the alpha phosphate of the NTP. Whereas the second magnesium ion bonds with the pyro phosphate of NTP. Well, this is correct. That is what we see going on here. Go ahead and highlight that. And then we can also go ahead and eliminate choice D which is none of these since we do have a correct answer. And finally, to be thorough, let's take a choice. C magnesium ions aren't involved in the elongation process. Well, that's not a correct answer. As we see, they are crucial to this elongation process. So again, which the following is correct about those 1st and 2nd magnesium ions choice be the first magnesium ion bonds with the alpha phosphate of NTP. Where is the second magnesium bonds with the pyro pyro phosphate of the NTP? See you in the next video.