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Main content
Current time:0:00Total duration:8:57
AP.BIO:
SYI‑1 (EU)
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SYI‑1.B.2 (EK)
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SYI‑1.C (LO)
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SYI‑1.C.1 (EK)

Video transcript

so I have drawn four different triglyceride molecules over here and some of you might be saying wait wait I thought triglycerides they involved all of these carbons and hydrogen's and oxygens well I see the oxygens over here but where's all of the carbons and hydrogen's and my answer to you is that they will be implicit this is a shorthand way of diagramming out these large molecules and you'll see this many times when you take chemistry biology organic chemistry and what's happening here is that each of these I guess pointy parts of this chain each of these vertices there's implicitly a carbon there's a carbon there there's a carbon there there's a carbon there and there's also if we don't if we don't put a letter at the end of the chain there's also a carbon right over there so implicitly there's a carbon there there's a carbon there there's a carbon there now you might also be wondering well what about the hydrogen's well we assume that every carbon is more covalent bonds and so if there's extra covalent bonds for each of these carbons we assume that those covalent bonds are with hydrogen so for example this carbon right over here it has two covalent bonds so the other two covalent bonds must be must be with hydrogen's same thing for this carbon right over there must be bonded to two hydrogen's this carbon the way it's drawn we only explicitly see one covalent bond so there must be three covalent bonds there must be three covalent bonds two hydrogen's so the carbons and hydrogen's are all there they're just implicitly there now you might notice and actually if you don't notice I encourage you to pause and think about what the difference is between this triglyceride this triglyceride this triglyceride and that triglyceride it might jump at you pretty quickly what jumps out at you is this triglyceride has no double bonds this one has one double bond this one has several double bonds and this one also has several double bonds but these two are also different we're going to think about the way that they're different you might you might immediately see that they this one is this one kind of kinks and curves while this one is able to stay relatively straight and actually that is the main difference and we're going to talk about it in a second why that is but first let's talk about this one when you have all single bonds one way to think about is that you have put as many hydrogen's onto these carbon chains as you can or another way of thinking about it is we have saturated this this fat with hydrogen's and that's why this is called a saturated fat a saturated this is a saturated fat this is something that you might have heard of this is referring to things like like like butter thing a lot of different fats that we tend to associate with being solid at room temperature and the reason why they're solid at room temperature is because these are all you know these are all bonded to these hydrogen's there's no kinks formed due to the double bonds these are able to be relatively dense which allows it to be solid or typically solid at room temperature and these are sometimes associated well we don't want to get into the whole nutritional battles about saturated fat and fats good or bad but these are sometimes associated these are sometimes called your your bad fats but as we'll see they aren't the worst fat so the worst fat are actually this one right over here but we'll talk about that in a second so this is saturated fat because way to think about is this saturated with as many hydrogen's as possible now this one on the right and another thing but it has all single bonds now over here or all single bonds between the carbons now over here we see a double bond we see a double bond between that carbon and that carbon and because of that instead of this carbon it already had this carbon already has three covalent bonds so it's only going to be bonded with one hydrogen this one already has three covalent bonds so it's all you're going to it's only going to be bonded with one hydrogen as opposed to two like these characters over here and because of that we don't have as many hydrogen's on the chain as possible so we consider this to be an unsaturated fat unn unn saturated unsaturated fat we don't have as many hydrogen's as possible and because of that unsaturated fats and especially polyunsaturated fats the these double bonds they tend to form these kinks in the structure which keep the molecules from getting really really dense which tends to make the liquid or more likely to be liquid at room temperature so this is an unsaturated fat this right over here we have multiple we have multiple double we have multiple double bonds in play this is called a poly unsaturated fat poly unsaturated unsaturated fat and since this actually only has they're both unsaturated fats this is a poly unsaturated saturated fat and only has one double bond we could call this a mano a mano unsaturated fat so these are both unsaturated fat this is many times happening so poly this is happening once so we would call it a mono unsaturated fat now one question you might have is well you know why are these why are the kinks forming for this molecule in this molecule and why are they not forming with this molecule even though this one has double bonds as well and this goes to our good friends cysts and trans and so you might remember if you have a double bond between carbons and let's say that you have let's say that you have you have one configuration let's do it let me just do it this way let's say you have one configuration where this is attached to some type of a carbon chain and let's say that this is a hydrogen then on the other side the rest of the carbon chain it could be in one of two configurations the rest of the carbon the rest of the carbon chain could be on the same side as the carbon chain on the left so we'll put our prime there and let me do that in that same color so you have your you have your hydrogen so this is one configuration now another configuration would be carbon double bonded to carbon you have your hydrogen but now the hydrogen's on our are on opposite sides and and your chains are on opposites or the rest of the carbon chains are on opposite sides and as we've talked about before this is because double bonds are rigid you can't rotate around it so it matters these are actually different these are actually different isomers right over here depending on whether this chain is on the same side as this chain or whether it's on the same side what's on the same side we call this a sis configuration this is a sis configuration and this is a trans trans configuration and it turns out that most naturally produced unsaturated fats are in the sis configuration and because they're in the sis configuration whenever you have these double bonds it forms it makes the chain actually bent and if you have many of these double bonds it makes it bend a lot and so polyunsaturated fats are even more likely to be liquid because it's very hard to pack them so what's going on over here well these are actually the configuration where the I guess you could say the rest of the carbon chains are on opposite sides of the double bond notice this carbon chain it might be a little bit hard to see is above the double bond we we form a covalent bond going upward there while while this carbon chain right over here is below the double bond and because of that it doesn't form a kink and these are in the trans configuration and so this right over here this is called a trans fat this is called a trans trans fat and they out they are typically found they aren't typically found in nature now it's interesting about trans fats it's a lot of folks said hey you know okay so that may be saturated fat is bad for us maybe we shouldn't eat as much butter and all of that and some of that's even up for debate these days and I said well what if we what if we started with unsaturated fats which are typically viewed as more healthy and our polyunsaturated fat and were to just throw a bunch of hydrogen's on them maybe not to change not maybe not to fully saturated but enough hydrogen so that some of these double bonds disappear and so it's more solid at room temperature which might make it a good replacement for for butter in cooking and a lot of the kind of the the shortening that you might have seen even 10-15 years ago or even today in a lot of places it says that they are essentially trans fat and so what happened is is that yes you can replace some a lot of these you can start to saturate it more with hydrogen's but that process also turned some of these turn some of the the cysts double bonds into trans double bonds and at first people thought oh that's harmless this is probably good for you it's you know it's still unsaturated but it turned out but it's but it has some of the properties of a saturated fat it's nice and solid and buttery and all of that and maybe it's even cheaper to produce you could kind of take it from other oils but it turns out that this is very unhealthy there's a lot of debates in nutrition but this is unequivocally unhealthy this does not exist in nature and it has all sorts of bad impacts and that's why a lot of states and even countries have now banned have now banned trans fats they actually some people I've gone I've even heard people go so far say this is actually you know poisonous to your body in certain ways that it really affects you in extremely negative ways that might be extra strong language but I'm I guess I'm trying to scare you a little bit don't eat trans fats anyway hopefully you enjoyed that
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