Now I want to show you guys some easy ways to memorize the structures of a few of the important monosaccharides. So guys, in biology, pentoses and hexoses are really highly prevalent. And you probably need to know a few of these, but you probably also don't need to know all of them. So for example, guys, for the hexoses, there are so many; there are like 16 different hexoses with all common names that are different from each other. There are lots of pentoses as well. This section is going to depend on your professor. Your professor may want you to memorize all the aldo hexoses, in which case this video is not going to help you very much, but most of the time, professors don't care that much about the exact names, and they just want you to be familiar with the most important structures. So that's what I'm going to try to do here; I'm going to try to summarize just some of the most important structures and give you guys easy ways to memorize them.
So just so you guys know, first of all, biological systems tend to recognize D monosaccharides more than L monosaccharides. So, all the structures we're going to talk about, pretty much for the rest of this section, are going to be D sugars. Okay? We're not going to talk about L sugars anymore because they're not really used a lot in biology, okay? So really, one of the most important pentoses that you need to know is ribose. So, what I did was I took out all the Os and all the Hs so that we can write them in together as we memorize it. Okay? So D ribose would obviously have the last O towards the right because it's a D. But then, where do the other Os face? Well, this one is easy because it has a nickname or like a little saying. What you can say is that ribose is alright, and what that means is that all the Os are to the right. Okay? Ribose is a very important pentose because it's the backbone for DNA and RNA. Remember it's called deoxyribonucleic acid and ribonucleic acid, so it's made out of a ribose. So you need to know about ribose. And then the other sides would just be Hs. So "ribose is alright". Easy enough, right? Cool.
All right. So now let's talk about glucose. Come on guys, glucose is super important. How do you draw glucose? Well, we know that a D-glucose would have the last O facing to the right, but then where do the other 3 go? Okay. Well, guys, this one's a little bit obscene, so I'm not going to do it on camera, but this is one of the ways that I found online that most students remember glucose. So go ahead and take your hand, take your right hand, and put it in front of you. I'm going to do this off camera and make a fist. So make a fist like this. Now go ahead and flick yourself off. Okay? If you saw it right, you saw a little bit of my hand come up. Now look down at that and notice that that's actually going to show you your positions. That's going to show you your 2, 3, 4, and 5 positions where your finger that's being very rude to you right now is one of the Os. So glucose guys, it flicks you off. So it's going to look like this O, O, and O. So those are your 4 fingers being represented by glucose giving you the big middle finger. Okay? And that's what it's telling you, you know, right around the holiday season or, you know, right when you're going to go out and splurge on sweets it's saying hey you're going to regret this later. So the Hs are just going in opposite places. Cool. So guys, those are ribose and glucose, super important.
But there are others that come up pretty often as well, and thankfully these can just be thought of as related to the other ones that we learned, especially glucose. So mannose, we've already dealt with it earlier. D mannose is just the C2 epimer of glucose. So we're going to draw again, remember that it had the O, the O, the O. But the C2 epimer changes at one position switched, so then I would put this O over here; that would be D mannose. D galactose would be the C4 epimer of glucose. So that means I'm going to draw all the other positions exactly the same. Remember this one's flicking me off over here. But now, in this case, I'm gonna actually get flicked off by 2 fingers in the middle here, so that would be the C4 epimer, which is galactose. And then finally, I'll take myself out of the screen here. And what you're going to see is that D fructose, so fructose is very important, but it's a ketose, and it's actually going to be the ketose of glucose. So think about that; this was glucose, let's draw in all of the different Os that you would expect for glucose. H H H H. But then remember guys that ketoses need to form on that second carbon in order to qualify as a ketone, right? So that means that this one here just becomes a ketone and this would be called D fructose, which is a 6 carbon ketose, okay? Specifically, it's the ketose of glucose. Okay?
Now guys, once again, I don't know exactly what your professor wants. This might be more than your professor wants. Your professor might not want you to memorize a lot of structures, or they might want you to memorize a ton. I'm just trying to help you with the most important ones, and if you need to know more than this, then there are other videos that might be able to help you. Okay? This is just like a basic overview of the most important ones and hopefully, you found this helpful. Alright? So let's move on.
