Nucleic Acids - Video Tutorials & Practice Problems
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Nucleic Acids
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So in this video we're gonna do a quick recap on nucleic acids, so recall that nucleic acids are actually one of four major biological macro molecules that compose all cells. So recall from your previous biology courses that the other three are proteins, carbohydrates and lipids, and we'll talk about each of those in separate videos as we move forward in our course. Now recall that nucleic acids, one of their major functions, is to store and encode hereditary information. And by hereditary, we mean that it could be passed on from one generation of life, down to future and newer generations of life. And examples of nucleic acids include DNA as well as our name. But it also includes a T. P. And 80 p is a denizen triphosphate, and we know it's the high energy molecule of the cell and entered cells use it for energy purposes, and we'll talk a lot more about eight p later on in our course. But for now, we're gonna be focusing on DNA and RNA. Now, recall that nucleic acids are polymers of nucleotide monitors. So what that means is that, uh, nucleotides are the monomers of nucleic acids and nucleic acids have directionality and the directionality is referring to when we have a chain of a nuclear kassid. The ends of that chain are different. And in, uh, nucleic acids, those ends are the five prime and and the three prime end. So let's take a look at an example. And in our example, what we see is we have a bunch of nucleotide monomers on left and through a process, were ableto link all of those nucleotide monitors together to form a nucleic acid polymers and notice that our nucleic acid polymer has directionality. It has a five prime end on one side and a three prime end on the other. And so, in our next video, what we're gonna do is do a refresher on the nucleotide monomer itself. So we'll pull out one of these guys and we'll take a look and analyze the monomer. So I'll see you guys in that video
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The Nucleotide
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So now that we've refreshed that a nucleotide is the monomer of a nucleic acid, let's now cover the nucleotide itself. So recall that a nucleotide monomer has three different components. It has at least one phosphate group. It has a pento sugar or a five carbon sugar, and it has a nitrogenous base. And so, in our image below, what we'll see is we're going to compare DNA RNA nucleotides. And on this left image we can see that we have a phosphate group shown by this group. Here we have a pento sugar that's shown by this group, and we have a nitrogenous space shown by this group over here. So we've got all three different components and we've got a nucleotide and in particular, what we have is a ribose sugar. And because it's a rival sugar, that means that at this position, what we have is a hydroxyl group or an oxygen bounded to a hydrogen group. And so this is a nucleotide of a wry bow nuke laich acid or an R and a molecule. So this is an R n a nucleotide. Now, over here on the right image, we see that we also have a phosphate group, a pento sugar in a nitrogenous base. However, this particular Pento sugar is a d oxy reboots sugar. And so the D here means without and the oxy means oxygen. So the D oxy reboots is missing one oxygen in comparison to the ribose sugar. And so at this position, instead of having a hydroxyl group, it just has a hydrogen atom here. And because of that, this molecule this nucleotide, is from a d oxy righ bow nuke laich acid or from a d n A molecule. So this is a DNA nucleotide. And so, in our next videos, what we're gonna be talking about are the nitrogenous bases themselves. So we'll talk about the nitrogenous bases, and we'll talk about how they base pair and the different types. So I'll see you guys in the next video.
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Nitrogeneous Bases & Base-Pairing
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So now that we've reviewed the nucleotide monomer, we could talk about the nitrogenous bases and the base pairs they form and DNA and Arnie. They differ in several different ways, including the nucleotides and the nitrogenous bases that they use. But we'll talk about the differences between DNA and RNA and our next video. Now, in this video, I want you guys to know that there are five different nitrogenous bases that could be grouped either as pira meetings or as pure rings. And these nitrogenous bases compare with one another via hydrogen bonds. And they do so according to Watson and Crick, base pairing rules where Recall Watson and Crick are the names of scientists that helped discover the rules. So if we take a look at our example below notice, the five nitrogenous bases are lined up horizontally, cytosine, thiamine. You're still Adnan and Wani, and these can be abbreviated by the first letter of the nitrogenous base. Now, I don't want you guys to memorize the structures of these nitrogenous bases just yet. In this video, I just want you to know how they're grouped. So notice the first three nitrogen spaces are grouped as pira meetings and the next two are grouped as periods. So you might be asking, Jason, how am I supposed to memorize how these nitrogenous bases air grouped? And I could tell you what helps me memorize it. And so pi remedies means pie. Kind of sounds like a pie. And so up here, I took a picture of a pie that my mom baked for me last week. No, I'm just kidding. I got this from the Internet, but notice how this pie has a single ring structure to it, just like the pie remedies do. And if we compare that to the pure ings, on the other hand, they don't have a pilot structure. They have a double ring structure that doesn't look like a pie. And so pi remedies have a single ring pie like structure. Now, the other thing that helps me to remember is that pirate meetings has a why in it, and so does cytosine and timing and wise air unique letters to these two nitrogenous bases. And I know that side of scenes and diamonds are pie remedies because they have wise in them. Now your cells do not have wise in them. However, we know from our previous bio courses that your sales replaced by means and RNA molecules. So I'm already associating yourselves with I means and I know to group your cells with thy means as pie remedies. Now there there are only five nitride into space is and what isn't a pyre emitting must be appearing. So in the next section we're gonna talk about how these nitrogenous base pairs form how they pair with one another in a DNA molecule. And so recall Adnan's always pair with timings and site of scenes, always pair with Guan teens. And we've already mentioned that these, uh, nitrogenous bases pair via hydrogen bonds. However, what you may not have recalled is that Adnan's and time means they form two hydrogen bonds in the base pair represented by two dotted lines here, and guanine and cytosine form three hydrogen bonds in their base pair. And a good way to remember this is that side. A scene is the third letter of the alphabet. And so the C G base pair forms three hydrogen bonds, and that means the other base pair must be for me to hydrogen bonds. And so, uh, if we take a look at our DNA molecule over here. Noticed that the Adnan's always pair with diamonds and the guanine is always pair with city scenes throughout the entire molecule and also recall that DNA molecules have directionality. And so, if I indicate this is the five prime end of one strand, the opposite end of the strand must be the three prime end and also recall from your previous bio courses that the two strands of DNA molecule go in opposite directions. And so that is called anti parallel. So the strands are anti parallel. And what that means is, if this strand goes from five prime to three prime in this direction Thea other strand must go from five prime to three, prime in the opposite direction, which means that this is the five prime and and this would be the three prime end. And so in our next video, we're gonna compare DNA and RNA directly. So I'll see you guys in that video
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Comparing DNA & RNA
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So in this video, we're gonna do a quick comparison on DNA and RNA. And so, in the left hand column and light blue, we have DNA and in the right hand column. And like pink, we have RNA and so usually textbooks, color code DNA and RNA accordingly, where DNA is usually bluish and Arnas usually pinkish or reddish. And so in the first row. What we have is the strands, and we know that DNA is usually a double stranded molecule, whereas RNA is usually a single stranded molecule. Now for the structure and shape, we know that DNA usually forms a double helix structure. Which, of course, is this twisting, ladder type structure that we've seen in all our textbooks. Now the structure of our DNA varies greatly, and it depends on the nucleotide sequence of the DNA molecule, and so you can have a single stranded RNA molecule that actually folds up on itself and hydrogen bonds with itself to form complex structures and loops. Now the pento sugar of DNA is D oxy ribose and recall that the de part of deoxyribonucleic means without an oxy means oxygen and so deoxyribonucleic into sugars lack an oxygen atom in comparison to the pento sugar of Arna ribose. Now nitrogenous bases of DNA include Adnan's thiamine, cytosine and guanine, and Arna has the same exact nitrogenous bases, except it uses your cells instead of using thigh means. Now for the function of DNA, we know that it encodes hereditary information. And from our Abia Genesis lesson, we know that the RNA molecule is more functionally diverse. So RNA encodes hereditary information, but it also has catalytic functions. And there are these structures known as Ribas IMEs, which will talk more about later on in our course that are RNA molecules with catalytic abilities. Now the directionality of a strand. Whenever you're giving a nuclear nucleic acid sequence and the directionality is not indicated, you always assume the direction is from the five prime end to the three prime end, and that applies to both DNA and Arna. So five prime, too three prime now recall that DNA has two strands that go in opposite directions, and so this, of course, is referring to anti parallel strands. Now the number of nucleotides in a nuclear acid molecule, uh, depends on if it's DNA are usually DNA, are a large molecules that contain million's of nuclear nucleotides. But that depends heavily on the type of organism that it ISS. Now. Our name molecules tend to have hundreds to thousands of nucleotides, and so, in comparison, our DNA molecules are much smaller than DNA molecules. And so we'll be talking a lot more about DNA and RNA throughout our biochemistry course, and I'll see you guys in the practice videos.
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Problem
Problem
A) What is the assumed directionality of the nucleotide sequence below? Label the ends of the molecule.
A C G T C T A A A C G G C T A
B) Is the sequence above from a DNA or RNA molecule? How do you know?
C) Write the complementary sequence to the strand below (include the directionality).
A C G T C T A A A C G G C T A
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Problem
Problem
Which of the following nitrogenous bases is a purine?
