tinywow_video_to_text_65330986.txt

All right, so the last class we're going to talk about are lipids, and this is probably the most diverse class. The number of different types of lipids and the variability in their structure is going to be the most diverse out of the classes here. When you think of lipids, you think of something tha...

All right, so the last class we're going to talk about are lipids, and this is probably the most diverse class. The number of different types of lipids and the variability in their structure is going to be the most diverse out of the classes here. When you think of lipids, you think of something that's very non-polar, but you can have lots of structures that end up being non-polar, which is going to kind of explain the diversity. And so when you go through these different classes of lipids, you're going to need to know some things about them structurally, but also functionally, like where they serve their function and stuff like that. So when we talk about triglycerides, we'll talk about phospholipids, we'll talk about cholesterol, and steroids. We'll talk about those together since steroids come from cholesterol, talk about single lipids briefly, prostaglandins, and then terpenes. All right, so we're going to talk about triglycerides first, but before we can talk about triglycerides or phospholipids for that matter, we've got to talk about what they're composed of. And it turns out they're going to be both composed of a glycerol backbone, and one of the other structural elements, one of the principal ones, is going to be what we call fatty acids. And fatty acids are just long chain carboxylic acids, like this guy right here. So big, long chain of carbons, and at one is going to be a carboxylic acid, that is a fatty acid. Now, it turns out we often class these as being saturated and unsaturated, and that really comes down to whether it has double bonds or not. And so if you kind of take a look at this here, so if we kind of look at a couple of carbons here, like this one right here, there's a carbon here that's got one hydrogen, and here that's got one hydrogen. But if you go to the analogous carbons up top on the saturated one, each of those carbons would have two hydrogens. And so it turns out every time you put double bond in, you're actually killing two hydrogens, so to speak. You're losing two hydrogens in the process. And so when we say that a fatty acid is saturated, we're actually meaning that it's saturated with hydrogen atoms. It has the greatest number of hydrogen atoms possible. And it turns out when they're saturated like this, they have higher energy density, higher energy content. So it turns out they also end up most likely to exist as a solid at room temperature, whereas you get these unsaturated ones, whether it's a trans double bond, a trans fat, or whether it's a cis double bond like this one. So it turns out a trans double bond is going to put a little bit of a kink into the structure, but a cis double bond puts a huge kink into the structure. And that's going to have some profound implications. So when you start trying to line these up next to each other, you know, with a bunch of fatty acids, it turns out you're going to, when it's saturated, you can just line them up right next to each other, one in front of the other, and lots of interaction, lots of surface area over which they're going to experience intermolecular forces, so much stronger intermolecular forces result. But especially when you put a kink here, it's going to prevent these fatty acids from interacting over the entire length of the fatty acid in kind of a general sense there. So with lower overall surface area that's going to be participating in intermolecular forces, it's just lower overall intermolecular forces, and as a result, you know, it's not held together strongly and much more likely to be a liquid at room temperature than a solid all of a sudden. So you can also have polyunsaturated fatty acids where you've got multiple double bonds, so even more so. But it turns out in the process of metabolism, so one of the first steps you do is you actually create a bond. So, and that's going to produce some of the energy you get when you're metabolizing fatty acids. So, well, if you already have a bond, well then you don't get that energy production, and that's why saturated fats are more energy rich, so to speak, you get more ATP out of them than these unsaturated ones. All right, so we're talking about fatty acids, one of the components in triglycerides, so now we can talk about triglycerides proper. So, and triglycerides have two classes of components, they're going to have three fatty acids, so then they're going to have glycerol, and you should know that they're held together by ester linkages. And so here we've got glycerol, glycerol is the same thing as one, two, three propane triol, so three carbons each having an OH, and then three fatty acids, and when you hook a carboxylic acid to an alcohol in a condensation reaction where water is produced, you create an ester, and so we get an ester right here, an ester right here, and an ester right here, so ester linkages holding these together, and so, so you can form, you know, between glycerol and these three fatty acids, you can form a triglyceride, or a triacylglyceride, or a triacylglycerol, also mamas, so, and form these, and you'd also form three water molecules at the same time, or you can go the reverse reaction, the reverse reaction's carried out by what we call lipases, they're the enzyme responsible in the body, so, and those lipases are going to hydrolyze those esters back into separate alcohol and carboxylic acid groups, so, but you should definitely recognize the overall structure of a triglyceride, the fatty acids that are attached here can be all identical fatty acids, it can be three different fatty acids, and all depends on where they're being used and things of a sort. Yeah, that's a lot of what I want to say there, triglyceride's being stored in your adipocytes, your fat cells, for me, right about here, for both energy and insulation. Alright, next class phospholipids, and phospholipids, very similar triglycerides, except, so still going to have glycerol backbone, here you've got glycerol three carbons, each having an oxygen, so, and two fatty acids, two other three locations, still got a fatty acid, but the third location is going to get some sort of phosphate group attached, instead that phosphate group's going to be very polar, phosphates themselves are negatively charged, so, but also you might, like this is, I believe it's phosphatylcholine, yeah, this is phosphatylcholine, which also has a positive aquatic quaternary amine, it's a positive charge over here, so you get this polar head group that's charged, and then you get these long non-polar groups that we call the fatty acid tails, or hydrophobic tails, so, and we form a phospholipid bilayer, which makes up your cell membranes, your nuclear membrane, and things of this sort, and in this case, your polar head groups diagram by a circle, they face out towards the cytoplasm, or towards the extracellular space, towards water molecules, and that since they're polar, they're great to go, and then the interior membranes where we sequester all these non-polar hydrophobic tails together instead. Also, you can kind of see the difference here between lipid bilayer form from saturated phospholipids versus unsaturated phospholipids, and again, when you put it up a bond in there, it's going to kink it, and again, even more so if it's a cis compared to a trans, but it kinks it, and all of a sudden now, your fatty acid tails don't line up as well next to each other, and so you don't get a bit of surface area over which they're experiencing this in a molecular force, and so you typically get a little more membrane fluidity when you start incorporating these unsaturated phospholipids into your membrane. So the next phospholipids here, very different from triglycerides and phospholipids, it's going to be steroids as well as cholesterol. We'll talk about them at the same time. Steroids are derived or synthesized from cholesterol, so we'll talk at the same time, so you can definitely see the similarities in the structure here. So, in this case, cholesterol here, you want to recognize it by its tetrasycle structure, notice the four rings connecting to each other, that is the hallmark of either cholesterol or something derived from cholesterol like a steroid hormone. So, if we take a look at testosterone and beta-estradiol, you can definitely see the similarities, you can also see that the tetrasycle structure, so it turns out that bile is also derived from cholesterol, so made-new liver, stored in gallbladder, helping in fat digestion and things of sort, but you can definitely see that it's related to the cholesterol structure. It turns out vitamin D, vitamin D technically is also derived from cholesterol, but vitamin D technically, a lot of people consider that a steroid hormone. I did not realize that, so it is the case, and it also has this tetrasycle structure, something worth knowing. I should also know that cholesterol, in addition to being used to make steroid hormones and stuff like this, is also a component of many cell membranes as well, and you can actually regulate the fluidity of the membrane by adding cholesterol. Now, most of the time, I'd like to think of it as increasing fluidity in a membrane, and it turns out at low temperatures it does that. At lower temperatures, membranes tend to go as fluid, and if you want to increase their fluid, you can put more cholesterol in there as well, but it turns out they also do the opposite of high temperatures, high temperatures, so cholesterol can actually add some rigidity into the membrane as well, but most of the time, when we think about what's the role of cholesterol in the membrane, adding fluidity, technically low temperatures, that's usually the context it's being brought up in. So, the next class lipids will talk about are single lipids, much less important than the ones we've already talked about, so I just want to really re-fill mention them, and you can recognize them based on their derivation from Slingosene, which looks like this, so they're all derived from this lovely molecule here, and there's gonna be some differences, you're gonna find out that you might attach a fatty acid right here, and you might also, in certain examples, attach either a phospho group or, you know, some sugars right there, and things of a sort, get different classes. Big thing you should know for these lovely single lipids, like a single myelin, they serve a variety of roles in the nervous system, so you kind of recognize their structure, but also know it and associate them with the nervous system. Next class lipids are the prostaglandins, and biggest thing you should probably just recognize that prostaglandins are a class of lipids, but outside of that's probably not the most important thing. They're all derived from rachidonic acid, making this lovely intermediate right here, and then this prostaglandin can be turned into a variety of different prostaglandin derivatives. There's some variety of functions, often autocrine and paracrine functions, so very localized hormones either on the same cell that released it or some neighboring cells, and big note, these are what mediate the inflammatory response, when you take a nonsteroidal anti-inflammatory drug, you're taking something that actually blocks the enzyme responsible for converting a rachidonic acid into prostaglandin, and if you don't have prostaglandins, well then you can't make the other enzymes down the chain that actually are mediating the inflammatory response, and that's how it reduces inflammation. So again, the most important thing probably here, probably not even the structure and stuff, like I was probably just knowing that prostaglandins are a type of lipid involved in some autocrine and paracrine functions like the inflammatory response. Last class lipids are the terpenes, and there are literally thousands upon thousands of different terpenes out there, especially in plants, much more prevalent in plants, but also in animals, and they're made from multiple, we call isoprene units, and these isoprene units are this little five carbon structure right here, and they're going to polymerize together forming a big long chain, and we can see, so one of the examples here is forming scalene and scalene is a precursor, it will start cyclizing on itself to form that tetracyclostructure notorious for cholesterol, so these terpenes are used in the synthesis of cholesterol, you can also see that beta carotene is a terpene, so you can see that big long conjugated structure explaining why it's colored in the space orange color, very conjugated, and you can also break it in half and use beta carotene to make vitamin A as well, both beta carotene and vitamin A also considered terpenes.