in this video we're going to focus on lipids so lipids would be the fats and oils that you've seen in everyday life these include fatty acids triglycerides phospholipids steroids waxes terpenes prostaglandins and things like that now lipids are nonpolar which means that they're mostly hydrophobic that is they don't mix well with water hydro means water phobic means fear and they try to stay away from water now lipids are mostly made up of carbon hydrogen bonds they're hydrocarbons now they may contain other elements like oxygen and sometimes nitrogen in the case of phospholipids and phosphorus too but for the most part they contain mostly ch bonds and ch bonds are nonpolar and it's because of the ch bonds that lipids are hydrophobic that they don't mix well with water now lipids such as triglycerides they're very useful for long-term energy storage if you're fasting if you're not eating for more than a day or so after your body burns out all the carbs the next thing that it looks for are the triglycerides in your system the lipids and it uses enzymes such as lipase to break down triglycerides into fatty acids and glycerol so that your body can derive energy from these molecules so they're very useful for long-term energy storage your body can go days without food as long as you have water you can go many days without food because of these triglyceride molecules they're very effective in stored energy in fact they can store more than twice the amount of energy compared to carbohydrates now lipids also play a major role in the cellular membrane in fact the cell membrane is mostly made up of phospholipids now lipids also provide thermal insulation and protection so they're very useful in the winter when it gets cold but now let's talk about each of these lipids one at a time so let's begin with fatty acids what are fatty acids fatty acids are long chains of hydrocarbons that contain a carboxylic acid functioning group at the end so here's an example of a fatty acid so this right here represents a carbon atom and those carbon atoms contain hydrogen atoms keep in mind carbon can only form four bonds so the carbon atoms in the middle have two hydrogen atoms whereas the one at the end possess three hydrogen atoms so as you can see a fatty acid is mostly made up of hydrocarbons the carboxylic acid portion of a fatty acid is the polar part so this is the part that likes water that's the the hydrophilic part and the tail of the fatty acid is the non-polar part so that is the hydrophobic part the part that doesn't like water now this type of fatty acid is known as a saturated fatty acid it's saturated in that it contains the maximum number of hydrogen atoms that you can pack on this molecule and there's no double bonds saturated fatty acids are solid at room temperature a good example of this would be butter an unsaturated fatty acid has a double bond so it looks something like this because of the presence of the double bond there's a kink in the structure this molecule it bends so that's an example of an unsaturated fatty acid for every double bond present you lose two hydrogen atoms unsaturated fatty acids tend to be liquid at room temperature so these would include the vegetable oils now another type of unsaturated fatty acid are the trans fatty acid in this configuration we have a cis double bond because the hydrogen atoms across the carbons that are double bonded are on the same side of the double bond in a trans fatty acid the hydrogen atoms on the double bond are on opposite sides so that's an example of a trans unsaturated fatty acid now let's talk about triglycerides so what we're going to do is take a three carbon molecule called glycerol glycerol has three hydroxyl groups and we're going to react it with three fatty acids the first fatty acid is a saturated fatty acid the second one is a monounsaturated fatty acid because we only have one double bond when you have multiple double bonds you have a polyunsaturated fatty acid a triglyceride is composed of three fatty acid molecules and one glycerol molecule now to make it we need a dehydration synthesis reaction so we're going to lose water the molecule will be these molecules will be dehydrated due to the loss of water so we're going to lose three water molecules and then we're going to synthesize a larger compound so it's a dehydration synthesis process and this will produce a triglyceride which looks like something like this now i might have lost track of the number of carbon atoms i had at the beginning but i just want to show you the general shape of a triglyceride so this is an example of a triglyceride so this molecule is very useful for long-term energy storage that's one of its major functions you can pack a lot of energy into this molecule the triglyceride is non-polar it doesn't mix well with water it doesn't have the polar hydroxyl groups so it can't hydrogen bond with water so to review in order to make a triglyceride we need to react glycerol with three fatty acids and that's going to make the triglyceride producing three water molecules and that is a dehydration synthesis reaction but now we can also go backwards if we want to the reaction between water and the triglyceride can produce glycerol and the three fatty acids going backwards the reaction is called a hydrolysis reaction hydro means water lysis means to split apart so we're splitting apart the triglyceride into its components glycerol and fatty acids now let's move on to our next category phospholipids these are lipids with a phosphate group so a phospholipid is made up of a phosphate group a glycerol molecule and two fatty acid chains in this example we have a saturated fatty acid and an unsaturated fatty acid the r group does contain a nitrogen atom by the way just in case you have a test question on that so phospholipids contain carbon hydrogen oxygen phosphorus and nitrogen phospholipids make up the cell membrane as you can see in this picture this is the phospholipid bilayer now phospholipid has a polar head and two non-polar cells the kink that you see in the structure is due to the presence of this double bond and the unsaturated fatty acid the phosphate group is polar so it likes water so that's the part that's going to be facing water the two fatty acid tails they don't like water so this is the hydrophobic region of the cell membrane that's the part that wants to stay away from water so this would be the inside of the cell which is aqueous it has water in it and this is outside of the cell but the membrane of the cell in the interior it's hydrophobic now the next category of lipids that we're going to talk about are steroids steroids contain four fused rings as you can see in the examples listed on the screen now the first one that we're going to talk about is cholesterol cholesterol is used to maintain the fluidity of the cell membrane on the upper right we have estradiol which is a type of estrogen the primary female sex hormone on the bottom left we have testosterone which is an androgen and that is the primary male sex hormone estradiol and testosterone they're chemically similar besides both having estradiol and testosterone are chemically similar besides both having four fused rings estradiol and testosterone both have this hydroxyl group at the top but estradiol really stands out due to the presence of this aromatic ring which is not present in testosterone or in cholesterol cortisol is another steroid hormone that is used to reduce inflammation by suppressing the immune system now let's say if you're stressed out you have a lot of exams to study for when your stress levels are high your cortisol levels will be high as well now when used as a medication cortisol is known as hydrocortisone so those are some steroids which are lipids that you may need to know now the next type of lipid that we need to talk about are waxes waxes are nonpolar they don't mix well with water waxes contain very long alkyl chains as you can see in this picture above but they can have many different functional groups here we have a paraffin wax with 31 carbon atoms the functional group is an alkane an alkane is an organic molecule that only contains carbon and hydrogen it doesn't have any double bonds so it's a saturated compound below we have a wax ester we still have two long alkyl chains but we do have an ester functional group so it's called a wax ester this one has 32 carbon atoms and 64 hydrogen atoms so these are very very long hydrophobic molecules some examples of waxes include beeswax i'm sure you heard of that one or the waxes that plant use to coat themselves in order to regulate evaporation and hydration and even candles candles are made up of waxes specifically the paraffin wax waxes have very high melting points this particular paraffin wax has a melting point of 99 degrees fahrenheit and it's boiling point it's 698 degrees fahrenheit so at room temperature waxes are solids but if you raise the temperature you can melt them into a liquid now the next type of lipid that we need to talk about are terpenes the basic unit of a terpene is isoprene isoprene has five carbon atoms and it's a diene whenever you see the suffix in that tells you that it's an alkane it has a double bond dye means two so a diene is a substance with two double bonds trine would be three double bonds other examples of terpenes include mercine and limonene which is found in appeals of citrus fruits and then we have beta carotene so this is found in carrots mercine has 10 carbon atoms so therefore it has two it's made up of two isoprene units so terpenes typically have carbon atoms that are multiples of five now here's a pop quiz for you or a test question how many isoprene units are needed to make a beta carotene what would you say what you need to do is count the total number of carbon atoms in beta carotene so you can pause the video and do that but you should get 40 carbon atoms and all you need to do is divide this by five this will give you the number of isoprene units that are needed to make beta-carotene so in this case that would be eight isoprene units if we look at limonene it has one two three four five six seven eight nine ten carbon atoms so ten divided by five will give us two so it takes two isoprene units to make up limonene limonene is an example of a cyclic terpene because it has a ring so that's it for terpenes another type of lipids that you may need to be familiar with now let's move on to our last category icosanoids so there's three categories of icosinoids that i'm going to talk about the prostaglandins the thromboxanes and the leukotrienes the prostaglandins have a five carbon ring and they have a total of 20 carbon atoms the thromboxanes they have a six membered ether containing ring the leukotrienes even though they have four double bonds they have three conjugated double bonds these are double bonds that alternate with single bonds so these are all lipids and notice that they all have a carboxylic acid functional group prostaglandins are used as vasodilators they can widen blood vessels they can also inhibit platelet aggregation thromboxanes they kind of work in reverse thromboxanes they can facilitate platelet aggregation they have a role in clot formation and in addition they work as a vasoconstrictors which means they can make the blood vessels smaller they can cause it to be more narrow leukotrienes are like signal molecules they serve as inflammatory mediators so those are some of the functions of these three types of icosinoids so that's it for this video that's all i got thanks for watching and if you like it don't forget to subscribe