this is the video for B 1.1 on carbohydrates and lipids and we'll focus specifically on lipids lipids include a wide variety of molecules but they are all hydrophobic so Hydro meaning water phobic meaning hating these all hate water and that is because they are nonpolar so because they are non-polar that also means that they are not soluble in water some examples of lipids include fats oils waxes and steroids and as you can see they have a variety of structures and they're going to have a variety of functions in cells and in living organisms but all are hydrophobic now before we talk about how we're going to put different lipid components or triglyceride components together let's talk about fatty acid structure in general I think that will help us quite a bit so what you're going to see here in fatty acids are these carb carbon chains and we're going to see hydrogens attached to them and then on either side of the carbon chain we're going to see a carboxy group Co and a methyl group ch3 so even when some of these start to look different right like some are longer some are shorter some are bent some are straight don't forget they all have some things in common a carbohydrate or s a carbon chain a carboxy group and a methyl group on either end now one of the things that I can make with those fatty acids is something called a tri glyceride Tri meaning three so this is the combination of a molecule called glycerol with Three fatty acid chains so here is glycerol right here it's a three carbon molecule with three anchoring points for those three fatty acids and you connect the glycerol with the fatty acids using a condensation reaction so that will form a Cove valent Bond and again condensation reactions are the removal of water H2O okay the removal of water molecules and then this oxygen here will be left to share between the carbon of the glycerol and the carbon of the fatty acid now this molecule this triglyceride is entirely hydrophobic which means it's non-polar and it is not soluble in water now one of the things that I can make with those fatty acid chains is something called a triglyceride and tri means three this is a molecule that's made up of glycerol this is what glycerol looks like and one to three fatty acid chains so one two three and glycerol serves as kind of like an anchor poter an anchor molecule for these three fatty acid chains we're of course going to connect them or Bond them together by removing water in a condensation reaction so again H2O is what gets removed a water molecule and that leaves this oxygen to be bonded between both of those carbons and if I do that one two three times and remove three water molecules I'm going to get something called a triglyceride again that's glycerol with 1 2 Three fatty acid chains attached this is entirely hydrophobic so that's important this whole molecule all parts are water hating and that's going to be very different from phospholipids which are amphipathic so amphi kind of like amphibian part on Land part on water means that it has two different parts of its molecule with different properties so it will have both a hydrophobic region just like the triglycerides but it will also have a hydrophilic region now you're probably more used to seeing these um phospholipids drawn like this right so we may have seen them in especially if you've drawn like lipid by layers or cell membranes already and this is going to be comprised of glycerol two fatty acids and a phosphate group okay so if I were to highlight them for you here here are these um fatty acid Tails they are right here okay okay so those are my two fatty acids and this glycerol and phosphate group so those are going to help form this phosphate head up here and if I'm looking at that in this molecular diagram here is that head with the phosphate group and the glycerol and these two fatty acid Tails now this is very important because this phosphate head is polar and that means it's hydrophilic it loves water and and these fatty acid tails are nonpolar and hydrophobic and so this is one of the reasons why they spontaneously form a by layer with those two tails like of two different phospholipids pointing inward towards each other again because they're hydrophobic and that would look something like this um here are those hydrophobic Tails facing inwards towards each other and the hydrophilic heads facing outward um probably in contact with some kind of watery solution so again Form and Function being very apparent here with these amphipathic phospholipids now in thinking about these spotty acid Tails they aren't all identical they can come in several different forms and those are saturated mono unsaturated and polyunsaturated let's talk about saturated fatty acids first saturated fatty acids are going to look something like this one one okay well actually all of these are saturated fatty acid Tails but we'll take a look at this one um as an example you are going to notice that it is a straight chain that all of the carbons in the carbon chain are connected by single bonds and it just so happens to be that they're usually solid at room temperature so I like to remember my s's here saturated fatty acids are connected by single bonds they are straight and usually solid at room temperature unsaturated fatty acids are not going to be straight they're going to be bent there's going to be what we call a kink or bend in the chain and that is due to not having all single bonds but at least one double bond somewhere in the chain so this is an example of a monounsaturated fatty acid it is a fatty acid that has one mono means one double bond somewhere in the chain now carbon can only form four bonds so if two of those bonds are to be bonded with the other adjacent carbon that means we cannot put another hydrogen here or here so for example this carbon already has 1 2 3 four bonds so it looks like I have kind of some empty parking spaces if you will now these hydrogens are going to repel each other and since there's no equally repelling Force down here it's going to cause a bend in the chain that's not as important as just being able to recognize this when I see a bend in the chain I want to be thinking unsaturated you won't necessarily always see the this double bond it may not always be zoomed in like this you may just see a line with a bend in it so that's again what it's really important to remember that this Bend is indicative of a double bond and so I should be thinking unsaturated this is a mono uncurated fotty acid if I were to see something with many kinks in the chain right so maybe something more like this okay I would want to be thinking polyunsaturated right many double bonds or more than one double bond in the chain there are some examples of exceptions because of course here's a monounsaturated fatty acid right it has one double bond but no kink in the chain and that's because this is a trans fatty acid um and so just a little bit different these are on opposite sides of the chain so equal repelling forces and it straightens it out but for the most part if we're thinking about naturally occurring fatty acids we want to be thinking about these and I want to look for that kink in the chain so let's take a little bit deeper dive into that shall we so we're going to have what's called Cy unsaturated fatty acids and Cy means the same or aligned so these are hydrogen atoms that are aligned on the same side of the chain um on that spot where there's a double bond more on that in a second this is going to be most of our naturally occurring fatty acids for example like oils and when you're looking at the diagram you'll notice that they have a Bend or a kink in the chain okay that's going to be very different than the trans fatty acids so this is when the hydrogen atoms are on the opposite side of the chain and because of that it straightens Out The Chain these are mostly man-made they're not really naturally occurring and what it does is it helps to solidify that fatty acid but on the downside I mean it's more stable which is great for things like food products but but one of the downsides is that there are some health concerns there especially that they're more easily metabolized into things like cholesterol so again we can take a look at that this would be an example of a Cy monounsaturated fatty acid again hydrogen atoms are on the same side and I see that bend in the chain and this is an example of a trans monounsaturated fatty acid the hydrogens have been moved to opposite sides of the chain so let's go back to this concept of I triglyceride so I would take three of those fatty acids they can be different kinds and attach them to a glycerol molecule and I'm going to get this triglyceride and those are the primary components of a special type of tissue in our body called adose tissue adapost tissue is a fatty tissue we're going to find it like underneath of our skin and surrounding our organs it's not a bad thing we're supposed to have that um although good balance is the right way to go um but triglycerides are a really great storage uh molecule and they're super at storing energy specifically long-term energy so right in the adapost tissue underneath of our skin we have a lot of triglycerides and they're really amazing at storing energy for long term because they are very stable they are not soluble in water which means they don't affect osmolarity or things like the concentration gradients and they're very energy dense so they have nine calories for every gram compared to things like carbohydrates which only have four calories per gram so they are excellent excellent excellent molecules for energy storage in that atopos tissue and they're also wonderful for thermal insulation so here is one of my favorite animals this is the ringed seal and the ringed seal lives in a very cold like Arctic climate and and it has a lot of atap POS tissue underneath of its skin and we call this special type of um adapost tissue blubber and this is wonderful because triglycerides are not good at conducting heat water is a very good conductor but not things like triglycerides so they form kind of a barrier between the body heat in the center of the organism and that cold water on the outside and they kind of like form this preventative layer um which keeps the Heat and and causes um less heat transfer to be happening to the environment in addition to our adapost tissue right underneath of our skin we also have triglycerides that surround our organs and that's really great because they can help absorb shock which is a good protection so for example we have some bones surrounding important organs but there are others like think about maybe your kidneys that don't have have a bone surrounding them so that um triglyceride or atopos tissue forms an important shock absorbing barrier there as well now we've already talked about the amphipathic properties of phospholipids right that hydrophilic and hydrophobic region which allows them to form a lipid by layer not only is that a good way to compartmentalize a cell but it can also help determine its permeability or what molecules can pass through the cell membrane and which ones can't so polar molecules like glucose let's say can't get past those hydrophobic Tails those hydrophobic Tails don't like things that are polar or have a charge but some things like steroids are not polar they are made of nonpolar lipids so here's a great example um one of the steroid hormones is called testosterone not all steroids are bad they're actually many that are good including testosterone and it is a um combination of three six-sided rings and one five-sided ring but it is entirely hydrophobic it is a hydrophobic lipid based molecule and because it's hydrophobic it can pass straight through that lipid by layer those little hydrophobic Tails don't mind it because they're also hydrophobic and so this has huge implications for how different hormones work in our body so for things like steroid hor hormones they can go directly into a cell and we'll find them passing three straight through that lipid by layer other hormones like insulin that are not lipid based cannot pass through that lipid by layer and we'll talk about that in another topic but again theme be Form and Function okay how is this formed well it's hydrophobic lipid and how does that impact the function well by being able to pass through this membrane so important to keep your eye on that theme Here