Skip to main content
Pearson+ LogoPearson+ Logo
Start typing, then use the up and down arrows to select an option from the list.


Learn the toughest concepts covered in Biochemistry with step-by-step video tutorials and practice problems by world-class tutors

Review 1: Nucleic Acids, Lipids, & Membranes

Nucleic Acids 1


Nucleic Acids 1

Play a video:
Was this helpful?
Hi. In this video, Siri's will be going over the major topics for biochemistry exam three, including nucleic acids, DNA sequencing, lipids, membrane structure and membrane transport. Now let's get started with nucleic acids. Nucleic acids were made of three components phosphate groups, which you can see pictures right here, a five carbon sugar and that five carbon sugar will be ribose like you see on the left here if it's RNA and you can tell that it's ribose because it will have a hydroxyl group on the two prime carbon there. And if you are dealing with DNA, you'll have deoxyribonucleic, which is pictured here on the right, and you can see that deoxyribonucleic is missing. Ah, hydroxyl group on that to prime carbon there. Hence the d Oxy part of its name in In its place, there's just a hydrogen. Now, the, uh, code part of DNA comes from the nitrogenous bases that can be present, and they're actually five nitrogenous bases that will appear in DNA and RNA. Um, and they are going from left to right here. Adam mean Juanin Cytisine. You're a sill and thigh mean now, adding and guanine are pure ing's, whereas cytosine euros Ill inthe I mean are pi remedies means a nice way to remember the Puritans in the pyre. Imagenes is using the mnemonic device for adding and guanine pure as gold. And for the pyre imagenes, you use the pneumonic cut. Hi. And hopefully that will help you remember your appearance from your pie remedies. Now it's important to note that you're a still is Onley present in RNA and thigh Mean is Onley present in DNA. So I'm just gonna put RNA up there DNA here just so we know that one is present one and the other and the other and they essentially replace each other in each structure. So in RNA, you have your Ozil in place of timing and DNA. You have timing in place of euros ill. And there actually is a biochemical reason for that. And it has to do with the fact that if if cytosine which you can see right here, if cytosine is bombarded with UV light, this amino group can actually get damn innate ID and turn into a carbon eel like we see in euros ill. So basically cytosine can be mutated into euros ill by UV light Now, if, uh if this happens, it's hard for your cells to tell which is the mutation, because that new your Ozil looks like a normal base to it so it can confuse the cell. However, thing I mean has this method group there. So if ah cytosine gets mutated to a euros ill in DNA, your cells will be able to tell. And that's because, um, if cytosine gets mutated into euros ill, your cells know that your cells not supposed to be there because they're supposed to have timing and timing has that methyl group on it. So I know that's kind of a lengthy explanation, but just a nice little kind of side story as to why this is the case. Because often in science, we really want to think about those why questions now moving on nucleic acids air actually polymers and their polymers of nucleotides. And here we have two. You get a little careful about our language because, um, because we're gonna use terms that sound quite similar to each other but actually mean different things. So nucleotides are like what you see here on the left. This is a nucleotide, and it's a nucleotide because it has a phosphate group present. Whereas if it did not have this that phosphate group like we see right here, it would be considered a nucleus side like you see, written there. So if you just have the pento sugar attached to the base, that's a nucleus side. If you have a phosphate group attached, it becomes a nuclear tied. Now, even though nucleic acids air made up of repeating nucleotides, you actually have to use nuclear tied try phosphates to synthesize them. And the reason for that is because, um, this bond right here this high energy bond between the, um phosphate groups will actually be cleaved to provide the energy for for the memorization reaction. DNA polymerase relies on the energy from the cleaving respond in order to continue synthesis. So even though technically new nuclear acids or polymers of nucleotides, you have to use nuclear tied try phosphates toe actually make them. And it's worth noting that nucleotides and course nuclear sides use a somewhat unique numbering system. So you might notice, looking over here at our sugar in our nuclear tied that all the numbers have a prime symbol next to them. So This is the one prime carbon, the two prime carbon three, prime carbon four prime and five prime. Now, the reason for that for using the prime symbol there is because the thief first carbon carbon number one is actually actually comes from the base, not from the sugar. So rather than starting this carbon at, like carbon number 10 In the case of this nuclear tied we have here, we started at one again and we just put a prime symbol there. So it's basically just to make the carbon numbering easier and to keep the numbers below 10. Um, you know, So this is a unique numbering system. Um, you probably won't really see anything like this outside of numbering nucleotides. Eso, You know, don't worry about it too much, but you do need to know the numbers of all the carbons in a nucleotide so moving on you can actually see down below. Here we have all of the bases and all of the bases have their carbons numbered and you can see that the carbon numbering of the bases is it's a little different between between the pure Eanes and the pie remedies. And again you need to know the numbering of all of these bases. Fortunately, you basically only have to memorize two numbering systems as the numbering for the pyre. Imagenes is consistent with each one. And likewise, the numbering with the pure ings is consistent with both of them. So you just have to memorize the peering and pie remedy numbering. And, of course, also know the numbering for your pento sugar. Lastly, these phosphate groups on the nucleotide um, the nucleotide triphosphate here. These, uh, these phosphate groups have their own naming convention. We don't just call it 123 We actually call this the Alfa Beta and gamma phosphate groups. So, uh, you know, a couple things to memorize here in terms of the numbering and naming of these molecules, and there's really no two ways about it. You just have to memorize this information because it's going to be important for the conversations down the line and for you to be able to determine the structures of molecules given a certain name. All right, that's all I have for this page. Let's move on