Subtitles section Play video Print subtitles Hi. It's Mr. Andersen and in this podcast I'm going to talk about nucleic acids. When I talk to students about nucleic acids, they're confused. They don't know what they do and they don't usually know what they're made up of. They do know that they're DNA and RNA but let's start with what they do. And so the biggest job the DNA and RNA have is making the proteins. The proteins inside the cell. And so when you look at me, you're looking at the proteins, but where are the directions to make those proteins? Those are found in the DNA. And how do they get to the proteins? Well they're shuttled out by RNA. And RNA is more of a worker that's making these proteins inside the ribosome. And so the first job they have is making proteins. What's the second thing they do? Well they make up our genes. And so that's what we pass on to the next generation. And so this is my son. He contains half of the DNA that I do. So I gave him a random half of my DNA. And my wife did the same. So he's a combination of me and my wife. And life has just passed DNA down generation after generation after generation. We've never found life on our planet that doesn't have DNA. That means that we're all connected through this single thread back to that first universal common ancestor. But what are they made up of? Those are nucleotides. And so these are the building blocks of DNA and the building blocks of RNA. So let's look specifically at one. So this is one nucleotide right here. A nucleotide is made up of three parts. We've got a phosphate group, that's going to be pictured right here. It's a phosphorus in the middle and then oxygen around the outside. Phosphate groups are really famous in biology. So they're the phosphates that are found in phospholipids that make the cell membranes of all life. And it's the same phosphate that we're going to find in ATP, adenosine triphosphate. It's the energy source. And in fact the adenosine triphosphate is exactly the same adenosine triphosphate that we add to make DNA. We'll get to that in just a second. What else do we have? Well, we have a pentosugar. Pentosugar means we have a five carbon sugar. In DNA that's going to be a deoxyribo sugar and then in RNA it's going to be a ribosugar. And then the most interesting part of a nucleotide is going to be the nitrogenous base. And it's called a nitrogenous base because it has nitrogen. And so most things in life are made up of carbon but there's going to be a lot of nitrogen here in the base of this nucleotide. And this is going to be different in each nucleotide. And so let's take a look at the nucleotides found in DNA. And so basically you have adenine, cytosine, guanine and thymine. And so we have four different bases and therefore we have four different nucleotides. And you can just see looking at them the size is going to be a little different on all four of these. In RNA they don't have thymine, you might notice. But they have uracil. It's going to look a lot like thymine but it's not going to be thymine. If we were to now look at all of those nucleotides together, so A, C, G, and T. And that's where the names come from. In DNA we're talking about these nitrogenous bases or these nucleotides. Now we've got uracil. Basically if we put them in order by their size we've got two major groups. We have these ones that have two rings and we call these purines. So this is adenine and this is going to be guanine. And then we have the pyrimidines and there just going to have one ring. So cytosine, thymine and uracil are all going to have one ring. So they're going to be smaller. And that'll become really important when we start bonding them together. So let's talk about bonding. How do you connect them together? Well when we talked about carbohydrates there's really only one way to connect carbohydrates. Or when we talk about amino acids, there's really only one way to connect them, but especially when we get to DNA you can connect nucleotides in two ways. So let's start with way one. Way one, we could put this one right underneath it so we've got an adenine and a guanine and then through a dehydration reaction we could lose a H2O right here and we could form a covalent bond between two nucleotides. And so if we were to add another one, we would add another nucleotide here, we'd lose a water and we're going to make another covalent bond. And so we can attach them together like that. And so that's what RNA is. RNA is a number of nucleotides simply in a row and they're connected with covalent bonds between each one. There's another way however when we get to DNA that we can bond them. And so let's say we have these two nucleotides, adenine and guanine, how could I attach this thymine right here? Well basically I can turn it upside down and it's going to form hydrogen bonds here between the adenine and thymine. And you've probably heard this before that adenine will always bond to thymine and guanine will always bond to cytosine. And that's why. There's going to be interactions between the oxygen, nitrogen and the hydrogen and make these hydrogen bonds that are connected with the two. And so when you're looking at DNA, let's kind of switch to this next slide. When you're looking at DNA, that's what's being connected right here in the middle. So that's going to be the hydrogen bonds between the nitrogenous bases on either side. And so why do we have DNA? Well we think life started with RNA because it contains a message, but overtime we kind of had two RNAs wrap around each other and we eventually had DNA. There's more to it that that, but DNA is going to be a more stable structure. We're going to have those hydrogen bonds here and then we're going to have covalent bonds between different backbones of the DNA as well. And so what are the backbone of DNA really made up of? It's just a sugar attached to phosphate to a sugar to a phosphate to a sugar. And so what are some differences between DNA on the right and RNA on the left? Well the first one would be the uracil versus the thymine. So that's going to be a different nitrogenous base. DNA is going to be a double helix and RNA is going to be a single helix. And then in life DNA is going to be found in the nucleus and RNA is going to be found pretty much everywhere that we need it. So if you're confused on how we go from DNA to proteins, or if you're really interested in the whole secret of life I'll put a little link to a video I made that kind of talks you through how we go from DNA to proteins. But the last thing I wanted to leave you with is how important they are. If you're interested in RNA and if you're interested in science and video games, then you may want to check this out. This is eterna. Eterna is a video game. I think it's centered at Stanford University and basically what they're doing is they're letting people on the internet build sections of RNA. And so basically you build sections of RNA. They have competitions each week and basically the winners each week, they will make your RNA. So they'll actually synthesize and make your section of RNA and then they'll see how it does. And so I'm going to launch the video game and talk you through the first level. And if you're interested in RNA or making things real in biochemistry you may want to give this a shot. So here's level one. Basically it's a tutorial so I can click on next and it will talk me through what I'm going to do. So you're going to build your own RNA. Let me click on the next one. The RNA is made up of four bases. Hopefully you know what that means now. Yellow base is adenine. Guanine, uracil and cytosine. And so as a warm up drill let's convert all the bases to guanine. So let me click here to start. So basically what you can do is go down here. I'm going to get my mutate and I'm going to mutate this to guanine. I love the music in here or the little sounds effects. Nice. So I cleared level 1. And then you can go to the next puzzle and we can just, going through, and so basically on this one what you can do is they will attract each other. So for example they're going to say that adenine and uracil are going to come together and that guanine and cytosine are going to come together. And so basically what you do is you get to play around with pairing these. And so I'm going to stop playing the video game in front of you, but give it a look. It's a really cool idea. People competing to make RNA and then they're actually building it in the real world. And so that's nucleic acid. It's incredibly important and I hope that's helpful.