4. Biomolecules
Nucleic Acids
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In this video, we're going to briefly compare and contrast DNA and RNA. And so recall that DNA is really just an abbreviation for deoxyribonucleic acid. And DNA, its primary function is to store genetic or hereditary information inside of the cell. And so this is information that would be passed down from 1 generation down to the next generation. Now we'll talk more about the functions of DNA later in our course. And in this video, we're mainly gonna focus on the structure of DNA. And DNA forms a structure that scientists refer to as a double helix. And so they call it a double helix because DNA is really going to be made up of 2 strands, and those 2 strands form a helix, a twisting, winding ladder type of structure that we'll be able to see down below in our image. And these two strands that make up the DNA molecule, they are actually antiparallel with respect to each other. And antiparallel just means that the directionality are going in opposite directions. These two strands go in opposite directions in terms of their directionality. And we'll be able to see the the anti parallel strands as well down below in our image. And these two strands, these 2 anti parallel strands, they're actually connected to each other via hydrogen bonds that form between the nitrogenous base pairs. And so, once again we'll be able to see this down below in our image. So on the left hand side of our image over here, notice that we're showing you DNA, deoxyribonucleic acid. And once again, DNA forms a double helix structure. And so, that means that it forms, it has 2 strands. So you can see one strand is right here and the other strand is right here. And these two strands, they wind up onto each other, forming, hydrogen bonds, between the base pairs. And so if we were to unwind the DNA so that it has this type structure down below, once again, you'll see the DNA, base pairs where, c's always pair with g's and a's always pair with t's. And so you can see the color coordination here and see how they always pair in that fashion. And so, this here represents 1 DNA strand, and, this down here represents the other DNA strand. And so, you can see that this blue structure that you see here represents the sugar phosphate backbone, and we know from our last lesson video that sugar phosphate backbones of nucleic acids have directionality. And so notice that this end of the sugar phosphate backbone for the strand is the 5 prime end, which means that the opposite end over here is going to be the 3 prime end. And so it's going from 5 prime to 3 prime left, from left to right in that direction. However, notice that the opposite strand over here, its 5 prime end is over here on the right, and so that, of course, means that its 3 prime end must be over here on the left. And so the bottom strand is going from 5 prime to 3 prime, from right to left in the opposite direction as the top strand. And so because we have 2 strands that are going in opposite directions, that makes these two strands in the DNA molecule molecule anti parallel with respect to each other. If they were going in the same direction that would make them parallel, but because they're going in opposite directions that makes them anti parallel. Now on the other hand, RNA is the abbreviation for ribonucleic acid. And RNA turns out it has a variety of different types of functions. And once again, we'll talk more about the functions of RNA later in our course. But one of the primary functions of RNA is to act as a template for synthesizing or building proteins. Now in terms of the structure of RNA, RNA usually forms a single stranded nucleotide chain rather than forming a double helix like DNA. So if we take a look at our image over here on the right hand side, notice that we're showing you RNA, which once again is usually a single stranded structure. So you can see the single strand of RNA right here. And, of course, the single stranded RNA is gonna have a sugar phosphate backbone that has directionality. And so if this is the 3 prime end over here, that means the opposite end must be the 5 prime end. And so, you can see that RNA, once again, it's specifically gonna be using nitrogenous bases of Us instead of using the nitrogenous bases of Ts like DNA. So t is once again specific for DNA, whereas u's is specific for are specific for RNA. And, the once again, RNA is normally a single stranded structure, but, the base pairing here can still apply if it, binds to, itself. Sometimes the RNA can fold up onto itself and bind to itself forming these complex structures. And, also RNA can sometimes bind to small, anticodons, which again we'll talk a lot more about later in our course. But you can see that this is how the RNA would base pair in the same way as DNA, except once again replacing the t, with the u, and that's really the main takeaway. And so this here concludes our introduction to the differences between DNA and RNA, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
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