Saturated fats, unsaturated fats, and trans fats | Biology | Khan Academy
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Saturated fats, unsaturated fats, and trans fats | Biology | Khan Academy


– So I have drawn four different triglyceride molecules over here. And some of you might be saying, “wait I thought triglycerides they involve “all of these carbons and hydrogens and oxygens”. Well I see the oxygens over here but where’s all of the carbons and hydrogens? And my answer to you is that they will be implicit. This is a short-hand 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 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 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 what about the hydrogens? Well we assume that every carbon has four 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 hydrogens. Same thing for this carbon right over there. It must be bonded to two hydrogens. This carbon, the way its drawn, we only explicitly see one covalent bond. So there must be three covalent bonds. There must be three covalent bonds to hydrogens. So the carbons and hydrogens 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. And it might jump at you pretty quickly. What jumps 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 and we’re gonna think about the way that they’re different. You might immediately see that this one kinda kinds and curves while this one is able to stay relatively straight. And actually that is the main difference. And we’re gonna talk about it in a second why that is. But first lets talk about this one. When you have all single bonds one way to think about it is that you have put as many hydrogens onto these carbon chains as you can. Or another way of thinking about it is we have saturated this fat with hydrogens. 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 butter. They’ve 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 this are all bonded to these hydrogens. There’s no kinks for them to do 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 with, I don’t want to get into the whole nutritional battles about saturated fat and fat’s good or bad. But these are sometimes associated these are sometimes called your bad fats. But as we’ll see they aren’t the worse fats. The worse fats are actually this one right over here. But we’ll talk about that in a second. So this is saturated fat because a way to think about it is it’s saturated with as many hydrogens as possible. Now this one of the right, and I don’t know anything about it it has all single bonds. Now over here, or all single bonds between the carbons. Over here we see a double bond. We see a double bond between that carbon and that carbon. And because of that, this carbon already has three covalent bonds so it’s only gonna be bonded with one hydrogen. This one already has three covalent bonds so it’s only gonna be bonded with one hydrogen as opposed to two like these characters over here. And because of that we don’t have as many hydrogens on the chain as possible. So we consider this to be an unsaturated fat. Unsaturated fat. We don’t have as many hydrogens as possible. And because of that unsaturated fat, and specially polyunsaturated fats, 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 them 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 bonds in play. This is called a polyunsaturated fat. Polyunsaturated fat. And since this actually only has, they’re both unsaturated fats. This is a polyunsaturated fat. And since this only has one double bond we can call this a monounsaturated fat. So these are both unsaturated fat. This is many times happening so poly. This is happening once, so we call it monounsaturated fat. Now one question you might have is why are the kinks forming for this molecule and 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 cis and trans. And so you might remember, if you have a double bond between carbons. And lets say that you have, lets say that you have one configuration. Let me just do it this way. Lets say you’ve one configuration where this is attached to some type of a carbon chain, and lets 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 I’ll put R’ there. And, let me do that in the same color. So 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 hydrogens are on opposite sides. And your chains, the rest of the carbon chains are on opposite sides. And as we 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 is on the same side. When it’s on the same side we call this a cis configuration and this is a trans, trans configuration. And it turns out that most naturally produced unsaturated fats are in the cis configuration. And because they’re on the cis configuration whenever you have these double bonds, it forms, it makes the chain actually bend. 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 formed a covalent bond going upward there. 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 fat. And they aren’t typically found, they aren’t typically found in nature. Now it’s interesting about trans fats is a lot of folks say “hey you know, okay, “maybe 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 they say, “what if we started with unsaturated fats?”. Which are typically viewed as more healthy, our polyunsaturated fat. And were just throw a bunch of hydrogens on them, may be not to fully saturate it, 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 butter in cooking. And a lot of the shortening that you might have seen even 10, 15 years ago, or even today in a lot of places, they’re essentially trans fat. And so what happened is is that, yes, you can replace a lot of these, you can start to saturate it more with hydrogens. But that process also turned some of the cis double bonds into trans double bonds. And at first people said, “oh that’s harmless, “this is probably good for you, it’s still unsaturated”. But it has some of the properties of a saturated fat. It’s nice and solid and buttery and all of that. And maybe is even cheaper to produce. You can 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 trans fats. They actually, I’ve even heard people go so far and say “this is actually poisonous “to your body” in certain ways. And 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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41 thoughts on “Saturated fats, unsaturated fats, and trans fats | Biology | Khan Academy

  1. One thing that has always puzzled me is whether the location of the "kinks" has any influence on health (plus or minus). Also how does margarine stay polyunsaturated and not be a trans-fat with what must be trans bonds to be solid??

  2. XXI education arises.

    I suffered my engineer bachelor with those dull classes, that can kill anyones attention.

    Under this format, visual attractive and appealing, quick and fluid, strong concepts, etc…
    This lead to expose the truth difficulty of the subject that is actually very low when you have all language elements already present in your memory.

    I'm really happy after enjoyed this video, I will stick to Khan as much as I can.

  3. 4:55 now i know where SJWS got the term Cisgender from and Associated it to the word transfat as is Transgender. You couldnt write this hahah.!

  4. Wow !! Excellent overview. You have changed my outlook on every new encounter I have when talking about fats. Now I get it.

  5. hey I recognize your voice from the economics videos. I learn a lot from your videos thank you!!!

  6. This video, and its first part are just fabulous! Gives you a complete understanding of Major kinds of fats with simple layman explanation. Thank you so much for this!

    Does anyone know who this teacher is?

  7. On page 23 there is a fantastic nutrition trick that will tell your body that you're not starving and keep your metabolic rate sky-high. Now this is going to shock you yeah there's a type of actual saturated fat yeah you know the kind the media tells you is all bad no this saturated fat is healthy and even supports fat burning metabolism.

  8. Q: Which has a better sex life, vegetable oil, or shortening?
    A: Vegetable oil, because it's more kinky.

  9. Dear Sir, within 9 minutes you were able to gave detailed information. Even normal people can able to understand. Excellent teaching sir

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