hi it's Kim and today I'm talking to you about lipids so we just talked about carbohydrates this is the second of the four macromolecules we need to talk about remember that lipids don't follow this General pattern of monomers linking together to form polymers there are no monomers of lipids and there are no Polymers of lipids so that's why on this table lipids you can see they don't follow this pattern of monomers and polymers so there aren't any names specifically for monomers and polymers what they do all have in common though is that they are all non-polar or hydrophobic and we learned this during the properties of water lecture when we talked about how water shapes non-polar molecules and we used phospholipids as our example remember phospholipids actually have a head region that's polar but the tails are non-polar and those taals are actually fatty acids so fatty acid taals are what make that part of the phospholipid nonpolar and fatty acids are one of the categories of lipids that we're going to talk about so are phospholipids I know we've already learned a little bit about phospholipids but I'm going to talk to you in a little more detail today about phospholipids so this is the list of lipids we're we're going to talk about fatty acids and triglycerides which are how fatty acids mostly exist in our body most fatty acids don't move around through our bloodstream just as separate fatty acids they're they usually exist as triglycerides we'll talk a little more about phospholipids we'll talk about cholesterol which is a lipid also and all the cholesterol based hormones and then finally waxes we'll talk about just briefly because they are significant in some living organisms and and they are in the category of lipids so let's start with the fatty acids and we're going to talk about two important types of fatty acids that exist in your body saturated fatty acids and unsaturated fatty acids these are both important and they are both used to make phospholipids so when you're putting phospholipids together to make cell membrane you use both saturated and unsaturated fatty acids to do that let's look at the structural difference but first I want to point out the differences between lipids and carbohydrates in basic structure because you do need to be able to visually recognize fatty acids or lipids just the same as you do carbohydrates so just a quick reminder that the carbohydrates and I'm just going to write carbs for short the carbohydrates the way you recognize those as being carbohydrates is first they had a carbonal group which remember was the carbon double bonded to an oxygen and then multiple hydroxy groups so those are the two ways that you recognized a carbohydrate lipids don't have a carbonal group or multiple hydroxy groups so the chain part of the lipid is just carbon and hydrogen and when you have a chain of just hydrogen and carbon or carbon and hydrogen oops I didn't really mean for that to go over this far so I'm just talking about this part just the carbon and hydrogen part right here this is called a hydrocarbon chain you've seen that term a couple of times now hydrocarbon chain is just a chain of carbon and hydrogen so you don't see any hydroxy groups on that chain the way you would if this was a carbohydrate also you have a different functional group right here so this one really kind of looks like a combination of car bonal and hydroxy and remember it's called carboxy so this is a carboxy group has the carbon double bonded to the oxygen but then it has the O also now you'll see this carboxy group when we talk about proteins also because amino acids also have a carboxy group but amino acids don't also have a hydrocarbon chain so you really need both of those Clues to tell you that you are looking at a lipid so remember fatty acids fall in the category of lipids on our list of macro molecules this top one is called a saturated fatty acid for a couple of reasons so I'm going to quickly erase what I've written and let's look at why we call one of these a saturated fatty acid and one an unsaturated fatty acid let's start by just looking at the basic differences between these two categories of f acid so when you look at this top one you can see the molecule the shape of it just goes straight across we call that linear this is a linear molecule versus this one has a band in the chain or a kink in the chain it's not linear so that's one difference just looking at the shape the reason the bottom one has a bend in the chain is because of that double bond between those carbons right here and unsaturated fatty acids have at least one double bond between carbons if you compare that with the saturated fatty acid at the top you can see that saturated fatty acid does not have any double bonds between carbons it's all single bonds so all single calent bonds between carbons sorry between wouldn't fit there so that should say between carbons but it wouldn't fit there and that's what makes that linear is the fact that it just has single Bond that double bond is going to cause the molecule to bend on either side it's a very rigid Bond now let's get to why it's called saturated versus unsaturated remember that carbon has to share four pairs of electrons to complete its outer electron shell and if we go to the saturated fatty acid at the top let's just pick this carbon you can see one two 2 3 four so every one of those carbons is sharing four pairs of electrons they're all single calent bonds and you can see we could we could say that these carbons are completely saturated with hydrogen they're holding as many hydrogens as they possibly can they're saturated with hydrogen saturated fatty acid now let's look at the carbons that are double bonded in the unsaturated fatty acid remember that a double bond counts is sharing two pairs of electrons so here we go one [Music] two 3 4 that carbon is sharing four pairs of electrons it cannot share electrons with another hydrogen it doesn't have any electrons left okay it's already sharing all four pairs so you couldn't put another hydrogen here okay that couldn't happen there are no electrons to share same with this hydrogen over here it's the only one because this carbon is double bonded so one two three four four pairs of electrons because these carbons are not holding the maximum number of hydrogens possible they're called unsaturated they're not completely saturated with hydrogen also notice that those two hydrogens are on the same side of the double bond as each other and remember that is called the Cy configuration geometric isomers involve carbon double bonded to carbon if it's on the same side whatever is attached to those carbons is on the same side of the double bond that is the Cy isomer and that's going to be significant when we talk about trans fats in a few minutes the normal natural configuration of an unsaturated fatty acid is the Cy configuration it's the Cy isomer okay that's just the basic structural differences between saturated and unsaturated fatty acids I want to show you this picture too so this show you the saturated fat also called the saturated fatty acid it's another name for it and you can see it's very linear and and this butter is shown here because we typically think of most saturated fats as being the animal fats so meat Dairy there are some vegetable fats though that are saturated but for the most part these are the animal fats lard okay versus unsaturated fatty acids we typically think of these as being the oils because they are not liquid at room temper I'm sorry they are liquid at room temperature they aren't solid at room temperature these are very linear molecules linear linear linear and so these can really pack tightly together and that's why these tend to be more solid at room temperature but when we're talking about the unsaturated fatty acid these are liquid at room temperature and that's why they're called the oils the reason they're liquid is this Bend in the chain doesn't allow them to Clump together so these tend to remain liquid at room temperature so we usually think of these as being vegetable or plant-based oils anything that we call an oil really falls into this C ategory so fats are an important energy source if you look at the amount of energy available in one gram of fat versus one gram of carbohydrate or protein you can see that it's more than double nine instead of four that's pretty significant if you eat too many carbs they go to long-term storage okay this is our storage form of energy this was very important in our Evolution so starting about two million years ago humans were hunters and gatherers they didn't settle down in one area and grow crops and and raise livestock they had to wander the land and eat what they could find and animal fats were a precious commodity they were very hard to come by having fat storage in your body was important because then you could go a long period of time without eating remember that our short-term form of carb storage is glycogen remember we store a certain amount of glycogen in the liver and a small amount in the skeletal muscles and that can be broken back down into glucose when it's needed but we don't keep a huge supply of that right we you know we keep maybe six to eight hour supply of that on hand if you have fat storage though you could go a week without eating You' be very hungry okay you would feel hungry but you wouldn't die of starvation if we had to have a constant supply of carbs and we didn't have this long-term energy storage then we would have to be eating constantly humans store more fat and other primates because we were hunters and gatherers we didn't just settle down with our troop in one location and stay there and use those food resources we we moved around and so it was an evolutionary advantage to have this fat store but we've learned that fats do a lot more than just provide us with energy storage f fats have a lot of other important functions in the body and this is just a short list of important functions that fatty acid have in your body fatty acids are incredibly important for developing children okay they need a certain amount of fats in their diet for normal growth and development especially for their nervous system their brain their immune system we need that fat for insulation so to conserve our body heat your joints and your sockets have a certain amount of of fat so your eye socket for example um has a lot of fat behind it even if you were to lose a ton of weight you would still have fat behind your eye socket because it's protective we need fat to protect our organs so you have a certain amount of of fat cells surrounding your organs to cushion them obviously for making cell membranes remember all phospholipids require fatty acids so we need a lot of fats for that think of how many cells you have in your body and how many phospholipids that must be and you need fatty acids for every single one of those phospholipids that's pretty crazy we just said normal growth and development obviously require um fat as we just said and then fat soluble vitamins okay so you have to have fat to help you absorb those vitamins in the intestines so a d e and K those are all fat soluble vitamins rather than water soluble vitamins this is what your fat cells look like under the microscope they're these you know Big Hollow vacuous cells you don't see a nucleus you don't see organel it's really just storage of those fat molecules so those fatty acid are just being stored in those cells and you you'll see that you know throughout your muscles or surrounding your organs again various places throughout the body we also know that these fat cells as part of our adapost tissue these adose cells release a lot of different hormones if you have an organ in the body that releases hormones it's called endocrine so endocrine organs okay sometimes they're glands release [Music] hormones and fat cells actually release hormones several different hormones that are important okay one of them is leptin and we're learning more and more about the role of leptin in obesity and that leptin is a signal to your brain for when you need to be hungry versus not be hungry so your fat cells release this leptin to tell your brain hey you have a big enough fat store you can stop eating if you're not releasing enough leptin then maybe you're going to keep eating even after you have a significant fat store so we're learning more about that but you can see this whole list of other things that leptin does it does more than just regulate appetite it activates immune cells it regulates your blood pressure your thyroid function your glucose function um in terms of releasing more insulin or not releasing more insulin your heart rate your bone mass different things are controlled by this hormone and it's released by your fat cells again there are other hormones released by your fat cells too but that's just the one I'm talking about today for the most part fatty acids don't just exist free in your your bloodstream okay we transport fats in our body as triglycerides so if you've ever had a physical and they've told you your triglyceride levels are high and this is what it's referring to so Tri means three and glyceride is referring to the glycerol molecule that is part of this so this is a glycerol molecule right here and through dehydration reaction so taking water o here H here removing that water dehydration reaction these fatty acids get linked to the glycerol three fatty acids connected to a glycerol that's a triglyceride again this is how you transport fats through your bloodstream to carry out all these other important functions that fats have in your body we have what are called essential fatty acids if something's called essential that means you must get it from your diet your body can't make those molecules so you're going to see when we talk about proteins we have essential amino acids these are essential fatty acids you have to have these for normal physiological function and they must come from your diet and I'm sure that you've heard the names of these before Omega 6 and omega3 so Omega 9 is non-essential and what that means is we can make that from other fatty acids so you don't have to get that from your diet but the Omega 6 and the omega-3 are essential again this is not nutrition class I'm not going to go through the whole list of foods that give you these but just know that these are a very very important part of your diet important for so many reasons and we're learning more and more about the health effects of not eating enough essential fatty acids um you can see here this is just a short list of what those essential fatty acids do normal brain functioning normal nervous system functioning production of important hormones regulating your blood pressure your blood viscosity Vaso constriction immune responses inflammatory responses cell membranes really important to get a certain amount of healthy fats in your diet so avocados fish all the different nuts different nuts have different types of essential fatty acids so like if you only eat cashews that's not good you might want to mix in some walnuts or almonds or some other kinds of nuts too so very very important what aren't important in your diet are trans fats so back in the 50s and 60s when humans first decided we're going to start Mass producing a bunch of junk food okay we're going to start making cookies and crackers and cakes and we want them to last a long time we want them to have a longer shelf life and we want peanut butter that looks all whipped up and pretty instead of separating into layers and having a shorter shelf life so they started manufacturing these fats that came from an unsaturated fatty acid so what they did is they took an unsaturated fatty acid and remember the Cy configuration this would be the normal natural version the Cy isomer and what they did is they did some a process called hydrogenation and what they did is they force this trans configuration and this trans isomer of the unsaturated fatty acid is linear it's linear like the saturated fatty acid was but it has a longer shelf life it's an artificial form of fat linear solid it temperature it gave these package Foods a certain taste that people really liked and really this is what kind of started the margarine generation and shortening I know when I was little our you know my parents thought well they were told butter is bad for you butter is cogging your arteries this new thing called margarine you can eat it it tastes kind of like butter you can cook with it you can bake with it same with this shortening like Crisco was the big thing like you go by the can of krisco and we use that for everything and we now know that it is killing us okay it's really bad it's not natural remember the body recognizes shapes your cells recognize shape so shape is so important here's my famous quote shape is key we have evolved to be able to process saturated and unsaturated fatty acids we do not have the ability to process the trans fats okay so you don't use these trans fats to build phospholipids you don't use these trans fats to build any structures or hormones or anything else in the body all these do is clog your arteries and kill you very very dangerous so dangerous that at some point the FDA realized this isn't good we need to basically make it illegal for food manufacturers to use trans fats they had to give the food manufacturers a certain period of time because they realized number one decreased shelf life okay you can't ship some twinkies and only have them be good for a month because by the time they get there they're going to be spoiled huge loss of Revenue you know millions of dollars of product being thrown away due to to that shelf life not being as long but also the flavor was different and people were used to a certain flavor so how are they going to account for that fast food restaurants they would fry everything in trans fats because you could use that oil multiple multiple times without having to throw it out and that was good right you if you can be McDonald's and fried those french fries you know for two months with the same bat of oil versus having to change it out daily that was a big deal so but they were so dangerous that the the FDA said we have to get rid of these now it doesn't mean that they have completely disappeared because if something says no trans fats on the label it just means it's below a certain amount so if you see anything that says partially hydrogenated or hydrogenated oils that means it still has trans fat in it so hydrogenated partially hydrogenated oils those are trans fats and I'll tell you Girl Scout cookies Girl Scout cookies I think I maybe they changed that this past year but they still had some partially hydrogenated fats you'll even see nutrition bars like if you look at protein bars it's surprising how many still have hydrogenated and partially hydrogenated fats if you're buying something in a box or a package that's already made you probably shouldn't be eating that okay that's not food you should be shopping the walls of the grocery store you should be eating fruits vegetables whole grain products Meats Dairy any of that stuff in the middle of the store that's fake food okay if it comes in a box are prepared for you probably not something you should be eating and this is one of the reasons I posted a bunch of slides about trans fats but really I've kind of told you everything that you need to know so they were inexpensive they lasted a long time they gave a desirable taste and and texture they raise your bad cholesterol lower your good cholesterol increases your risk of developing heart disease and stroke It's associated with a higher risk of developing typ type two diabetes so dangerous so again um just because something says um no trans fat it means it has less than half of a gram of trans fat per serving but remember you can look at the serving size on a package it's not the whole package okay serving size could be one tablespoon so if you have a half a gram per tablespoon and there's a big box that's that's a lot of trans fat in one product so really again look for partially hydrogenated or hydrogenated on the on the label when you're buying an already packaged product or here my better advice to you is don't buy anything that's already made in a package but again you know some of us grab those protein bars or whatever you know on the go it's a good quick easy lunch so really look at the labels on those okay moving on from fatty acids let's look now at the fatty acids that make up the phospholine lipids so remember these are phospholipids make up all of our cell membranes so the plasma membrane on the outside of the cell and all of the membranes within the cell all the membranous organel so polar head which is water leving hydrophilic hydrophobic Tails because those are fatty acids okay just looking at the shape of those two tails one is linear and one has a Bend do you remember what those two types of fatty acid are called okay so the linear one no double bonds between the carbons this is a double bond right here see that where that's drawn that's a double bond and you can see that bend in the chain so this would be the SAT at fatty acid wow I'm just really having a struggle with spelling today saturated and this one is unsaturated okay this is significant when you make a whole plasma membrane so so here's your cell okay the whole outside remember this is not flat your cell isn't flat like this is how we draw it on the board but the whole outside of that cell is covered in the plasma membrane that plasma membrane is regulating everything moving in and out of the cell we're going to learn a lot about that everything moving in and out of the cell is regulated by that plasma membrane which has some proteins that are regulating but also these phospholipids are regulating what's moving in and out certain things can't move past those non-polar tails for example because if something is polar it can't just move across those non-polar Tails but also the shape of this is really critical because this Bend in the unsaturated fatty acid if that's in a membrane it creates a space where certain molecules can slip through and that plasma membrane there's a term that we use associated with that we say that it's selectively permeable okay permeable means stuff can move through okay it's not completely keeping molecules in or out but it's selecting what can move through and part of this selector permeability is based on the fact that some of the fatty acid tails on those phospho lipids have this Bend they're the unsaturated fatty acids and that bend allows a little space where certain molecules can move through so an important part of that permeability is what ratio of saturated versus unsaturated fatty acids do we have if they were only saturated those fossil lipids would all be really linear and they'd all come right up against each other like this and there'd be no room for certain molecules to move through it's when we have suddenly this one has a bend in the chain and now we've got this little space where stuff can move through in and out of the cell so this shows you a phospholipid by layer but in this picture you can see that these are all linear so these would all be saturated oh goodness try this again these would all be saturated fatty acids you can see there's no space there I'm G to take you to this picture and you can see well they didn't really show the bin very well but this is showing you cholesterol but if you can imagine that if some of these had a bend in the chain it's going to create some spaces where stuff can move through versus all being linear I really wish now that I had put a better picture there to show you that so when we talk about the plasma membrane we we'll talk about this again this is just kind of an introduction to this topic of saturated and unsaturated fatty acids so you do use both of those to make your your plasma membrane you use both of those to make f phospholipids so that just goes to show you saturated fatty acids are an important part of your diet so you you know you need to get those somewhere because you need a certain number of saturated and you need a certain number of unsaturated fatty acids to make cell membrane so membrane fluidity and selective permeability is influenced by the phospholipids okay having one saturated and one unsaturated fatty acid tail creates just enough small gaps for some molecules to cross the B layer without it being too permeable what's what that's saying is imagine that they were all bent now you're going to have too many gaps because they can't pack in next to each other okay you want to have some of them close to each other so really having a combination of the two is really ideal so you do you use both saturated and unsaturated to make your plasma membrane both are important in your diet okay cholesterol cholesterol is another category of lipid um and cholesterol falls in the category of molecules called the stero steroids so when you hear steroid you think of guys with big muscles right but not all steroid not all steroids are anabolic so anabolic steroids primarily testosterone which is one of the hormones that are made from cholesterol so steroids are these four carbon Rings fused together so four fused carbon rings so they all look pretty similar to this and this is cholesterol cholesterol gets a bad wrap but cholesterol is an important part of your diet because it is used to make hormones and I'll give you a list of some of those hormones in a minute and it's also part of the plasma membrane so the plasma membrane is mostly phospholipids but you're going to see that it also has um cholesterol and it has some important proteins and there are some other things going on there also so here's more detail on the role of cholesterol in your cell okay we consider it a stabilizer in the plasma membrane okay so without cholesterol the phospholipids and plasma membrane would move around too much when we talk about the plasma membrane you're going to see that those phospholipids are fluid they move side to side they flip-flop with each other and they move around cholesterol stabilizes those phospholipids and keeps them from moving around too much so this is the picture I showed you before that cholesterol is a stabilizer in the plasma membrane it keeps those phospholipids from being too fluid and moving around too much without that cholesterol that plasma membrane would be too leaky because as those phospholes are moving molecules can slip through oops and is chemically modified into hormones what hormones are we talking about these are the hormones that are made from cholesterol they're what we call the steroid hormones steroid hormones sorry I need to sip of water that's what's causing me to talk weird Okay so there's the list obviously the first three we think of as being the sex hormones and it's very interesting to see just those subtle differences estradiol that's estrogen you can see the the shape of estrogen and testosterone are very similar that's because they're both made from cholesterol but just that subtle difference in shape dramatic difference in effect right estrogen causes completely different characteristics to develop than testosterone does Cortisol this is our stress hormone it's meant to be a natural anti inflammatory but if it's present all the time that's a problem and we're learning more and more about the effects of having too much cortisol around for for too long because cortisol is produced in response to physical stress so let's say you go for a long run and your joints and your muscles are sore and cortisol is going to be released as a natural anti-inflammatory it's the natural cortisone so when you get cortisone shot to reduce inflammation you're getting a synthetic version of cortisol you know that you can't get a cortisone shot 50 times right it's really damaging to the tissue if you get too much of it the same is true for natural cortisol if it sticks around for too long and you get too much of it it's actually very damaging and in fact um I want to show you this slide so cortisol is naturally made by your adrenal glands okay and it's made from cholesterol cholesterol is a lipid so cortisol is a lipid based hormone your adrenal glands are on top of your kidneys and cortisol does a lot of things but really is your it's your stress hormone it's supposed to reduce inflammation due to physical stress but it's also produced in response to psychological stress it controls your mood it it controls a lot of things and it's really part of your body's fight ORF flight response but it can we know cortisol can cause a lot of bad effects too because it is um used to manage how you use carbohydrates fats and proteins and we know that it controls your blood pressure it can can control your sleep and wake cycle so when you have too much of it it's bad and this is just a short list you can just read those for a second this is just a short list of things that can happen when you have too much cortisol around back probably about maybe eight years ago now the Natural History Museum had a Body Worlds exhibit where they had all these preserved bodies you could go look at and I was kind of leery about going I'm not an anatomy teacher and I'm still kind of squeamish about the cadavers so I wasn't super excited to go but I went with Dr Carpenter one of our most amazing teachers who just retired sadly for our students and I just remember there was a display that showed two brains one of a person who who had been subjected to an enormous amount of psychological stress and the Brain looked like a raisin from the cortisol that had damaged that person's brain cortisol can be bad you know it was meant to be and evolved to be a natural anti-inflammatory to reduce physical inflammation but now with our current world you know we have a lot of psychological stress and so we're constantly releasing cortisol and I just think that as humans the more we can just really put things in perspective and try to really relax ourselves and breathe and meditate and exercise and do things to really try to keep our cortisol production down the more healthy we're going to be in general and I mean again this is just a short list of things we know that happen based on having too much cortisol around okay obviously the other hormones are sex hormones and so again you need a certain amount of cholesterol in your diet because these are all oops these are all made from cholesterol which is a lipid so we would say that these are all lipid based hormones all of these including cortisol that is now written over I am so sorry I am just like an old person trying to use technology here okay these are all made from cholesterol and so we would say that these are all lipid based hormones meaning they're made from lipids okay because cholesterol is a lipid why am I telling you this this is important because we also have hormones that are protein based okay so hormones can be proteins or they can be lipids and the protein based hormones that we've already talked about two opposing hormones that we talked about with regulating our blood glucose levels insulin and glucagon are hormones but they're made from protein all of these hormones these are lipid based they're made from lipids what are hormones hormones are chemical Messengers they're produced in one part of the body and they have an effect in another part of the body so hormones are chemical Messengers they're usually produced by glands but they're also produced by organs and they're produced in one part of the body and they have an effect in another part of the body so for example insulin insulin is produced by the pancreas and it stimulates your cells outside the pancreas to take um glucose into your cells it also causes glucose to be linked together to form glycogen so it's released into the bloodstream and it travels to somewhere else to have an effect so these chemical Messengers are usually released into the bloodstream okay so estrogen produced by the ovaries doesn't stay in the ovaries it gets released into the bloodstream and it has an effect on other organs in the body so same thing for cortisol produced by the adrenal glands on top of the kidneys but released into the bloodstream and it has an effect throughout your whole body okay finally our last category of lipids are the waxes and waxes are really significant in a lot of different organisms so these are plant waxes and you can see the water beating up waxes are incredibly important in plants so implants they prevent drying out called desiccation which means drying out so waxes are really really important imp plants and waxes are lipids this little Cy here this frog frogs and other amphibians use waxes to keep from drying out so do a lot of different um arthropods so different you know insects crustations Etc use waxes for the same thing to keep from drawing out on land and other other functions of the waxes too these guys actually have little wax glands um on their back and they'll actually you can watch videos of them taking their back legs and moving the wax up over their whole body to keep them from from drying out and humans obviously we only have ear wax and that wax is to protect your ear canal from things crawling in there from other pathogens getting in dust dirt debris and insects worms keeps them from getting into your ears okay those are the lipids