Placeholder Image

字幕表 動画を再生する

  • 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.

Hi. It's Mr. Andersen and in this podcast I'm going to talk about nucleic

字幕と単語

ワンタップで英和辞典検索 単語をクリックすると、意味が表示されます

B1 中級

核酸 (Nucleic Acids)

  • 40 11
    Cheng-Hong Liu に公開 2021 年 01 月 14 日
動画の中の単語