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Video transcript

let's study the molecular structure of triglycerides try glycerides and in everyday language we often call these fats we often call these fats which is often kind of a feared word but as we'll see it's essential for life fat's in a liquid form it's sometimes referred to as oils and a more technical term for triglycerides this is triglyceride is the word that you might hear when you go to the doctor's office but it can also be referred to as try and I'm going to do the different parts in different colors try a so try acyl glycerol try acyl glycerol actually like this second name more because it makes sense when you break down the molecule try acyl tri acyl glycerol but triglycerides this is literally fat or what most people typically refer to as fat they're talking about triglycerides if you were to get your cholesterol checked or if your parents get their cholesterol checked they'll probably get a report on triglycerides which is really a measure of the fat concentration in their blood but let's think about what I try glyceride is and so here I have the constituent molecules of a triglyceride this this molecule on the left this is glycerol let me do it in that same blue that I wrote I just wrote glycerol in this is this is glycerol we can see we have a three carbon chain right over here each of those carbons is attached to a hydroxyl group and Oh H group if you just get it attached to one of them this makes you an alcohol so this definitely makes it an alcohol this sometimes called a trial and has three hydroxyl groups right over here and this is considered to be a sugar alcohol a sugar alcohol we see why it's an alcohol it's got its hydroxyl groups and it's also sweet if you were to if you were to drink a solution of glycerol it will actually be sweet and you might already be familiar with the word glycerol from the famous busch song glycerine glycerine is referring to glycerol glycerine glycerine so there you go that is a glycerol right over there and you form a triglyceride when a glycerol molecule reacts with three fatty acid molecules so these characters on the right these are each a fatty acid these are each a fatty acid this is one fatty acid this is another fatty acid this is another fatty acid now why do we call them fatty and in particular why do we call them a fatty acid well you have one part that has these big carbon chains here and I drew these dot dot dots because they can actually have different numbers of carbons they can have anywhere between up to-- you know there's based on my research you can have into the high 20s numbers of carbons in most biological systems you tend to have an even number of carbons and in an in most animal biology you tend to have 16 to 20 carbons and if it's an even number you're talking about 16 18 20 carbons involved in these fatty acids all the ones I've drawn has all have all single bonds so the carbons are we have as much as many hydrogen's bonded to it as possible but you could also have double bonds there and we'll talk about that more when we talk about saturated and unsaturated fats so you have this that you have this this carbon chain here that part is hydrophobic it won't dissolve well in water and that's why people tend to tend to refer to it as kind of fatty and then you have on the left-hand or at least the way I've drawn on the left-hand side you have a carboxyl group so this right over here this is a carboxyl group car box'll group and this is acidic it's very easy for it to donate a hydrogen because if it donates a hydrogen or a hydrogen proton I should say because if this oxygen takes those electrons that negative charge can be spread between this oxygen and this oxygen over here and so it's very willing to give away a hydrogen so that makes it acidic so that's where the acid comes from that's a fatty acid and when you have these three molecules they don't have to be identical this one could have 18 carbons this one over here could have 16 carbons this one could have 20 carbons it might have a couple of double bonds in it so they could all be different but let's think about how they actually form together like you know those robot movies from the from the 80s like like Voltron so what you have happening and this could be a little organic chemistry and this is really just a review of dehydration synthesis you have you have a lone pair in each of these oxygens these oxygens that are part of the hydroxyl group so let me draw that so you have a lone pair there or yes you have two lone pairs you have two lone pairs over there you have two lone pairs over there and so you can imagine a world where if they just bump past each other in just the right way this carbon over here is going to have a partially positive charge it has three bonds to two oxygens oxygens that are very electro very electronegative and so this guy if he just bumps into it in the right way these electrons could be used to form a bond with this carbon the one that has that partially positive charge and just as that is happening just as that is happening this bond could be let go this oxygen say okay look you already you got another you're sharing in another pair I've had enough of that I'm going to take these electrons for myself or even better I'm going to take them for myself or an eventually capture or or maybe I capture first it can happen in all different ways a hydrogen proton I'm going to capture a hydrogen proton and then I can become this this this collection right over here can become a water molecule and I'm doing this a very high-level overview of the mechanism you can go into more depth of this when you go into when you go to into organic chemistry but this could happen three times so it can happen again over here going to happen again over here this guy takes this takes let me do that in that same white color so he takes both of these electrons that he so badly wants to take back and maybe uses it to grab to grab a hydrogen a hydrogen proton it could happen the other way maybe grabs a hydrogen proton and then and then just as he's leaving this guy comes back so there's there's different ways that all of these can happen but this is the general idea and then you have it happening a third time down here one of these lone pairs come and do come and form a bond with this carbon this carbon in the carbonyl group part of this carboxyl group and so and so once again this guy can take those two electrons away and maybe share one of and share that pair with a hydrogen proton again this is forming a water molecule this is forming a water molecule so three water molecules are going to be produced this is why we call it dehydration synthesis we're losing three water molecules in order to form these bonds so what's it going to look like after this has happened well let me scroll down let me scroll down here and actually let me just zoom actually let me just scroll down here so this green bond over here is going to now so this green bond that's this big long curvy thing is this green bond and this second green bond is this green bond and this third green bond is that green bond and each of these the way I have the way I've drawn it right now each of these oxygens each of these oxygens haven't let go of its hydrogen's and that could actually happen before or after all at the same time chemistry actually is not a clean thing but I could if I want I could draw the hydrogen's here I could I could draw I could draw the hydrogen's I could draw the hydrogen's over here and then these would have a positive charge these would have a positive charge but then you could imagine another water molecule coming by and snapping kind of taking one of these hydrogen protons taking the hydrogen protons away from each of those oxygens and then you would be left with you would be left with this you would be left with this molecule right over here and remember we got we produced three water molecules so let's one one two and three water molecules and now this molecule if you ignore the water molecules out there this is a triglyceride this is let me write it again actually let me write them a little slightly more technical term sometimes referred to as tri acyl tri acyl glycerol tri acyl glycerol well we know where the glycerol comes from it has this glitter this glycerine or this glycerol backbone right over here now what is a soul mean well a soul is a is a functional group where you have a carbon that's in a carbonyl that's part of a carbonyl group it can be bound to a kind of an organic chain right over here I'll just call that R and then it could and then it's bound to something else and so we have three acyl groups so tri acyl so this right over here this right here is an acyl group this right over here is an acyl group this right over here is an acyl group each of them they're bound to an oxygen their bond to an oxygen right over here and actually that gives us a more practice with another functional group when you have when you have a situation let me get another color out when you have a carbon that is or you have a carbonyl group and let's say you have just an organic chain right over here and then you have an oxygen and then you have another organic chain right over there this this thing is called this thing is called an ester this thing is called an ester and you actually see three esters right over here so this you see this ester this ester right over here you see this ester right over here and then this ester right over here so this wasn't just practice and learning about fats or tri acyl glycerol or triglycerides these are all words for the same thing it's giving us good practice with these functional groups but now you see were try a solicitor all come from you have a glycerol backbone and you have these three acyl these three acyl groups that for allowed to attach to the fatty acids so that's what that's what fat is when when people are referring to it and this is just pictures of it this is this is coconut oil right over here it's it's right here it's it's below its melting point so it's in its solid form and this right over here I'm not sure which type of oil this is but it's past its melting point and so it's in its liquid form so people would typically refer to this as as an oil but this is made up of a bunch of triglyceride but this is a big mixture of triglycerides here and and if you were to see their molecules they would all have generally this shape but the fatty acids would have different numbers of carbons and might have different numbers of double bonds
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