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Saturated fats, unsaturated fats, and trans fats

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SYI‑1.C.1 (EK)
Saturated fats, unsaturated fats, and trans fats.

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  • starky ultimate style avatar for user alina
    Can someone please explain why the trans-configuration prevents the molecule from forming kinks? And why the cis-configuration allows it to form kinks? Perhaps I'm missing something. Thanks!
    (17 votes)
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    • old spice man green style avatar for user Matt B
      Are you familiar with alkanes and alkenes? Alkenes have carbon to carbon double bonds and prevent the twisting of the bond. When all bonds are single bonds you typically draw these tails to be these long carbon zigzags and that's OK because the bonds will rotate in such a way to keep the chain relatively "straight" (going to left to right). Once you include a double bond, twisting cannot occur, and then it greatly matter if you want to continue with the left to right zigzags, in which case you will need a cis-bond, but otherwise a trans-bond will force the chain to go in the other direction. If I am not clear enough, see if you can get your hands on a model kit or something to let you visualize the molecule in 3D.
      (4 votes)
  • aqualine seedling style avatar for user esther pincate
    Ok so in simpler terms what are saturated, unsaturated and trans fats?
    (4 votes)
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    • orange juice squid orange style avatar for user Cameron
      - Saturated fats contain only single bonds in the carbon chain, with all excess carbon electrons bonded to hydrogen.
      - Unsaturated fats do not have all excess carbon electrons bonded to hydrogen.
      - There are two types of unsaturated fats: cis and trans.
      - Cis-unsaturated fats contain double bonds, with hydrogens on the same side of the double bond which causes the carbon chain to bend.
      - Trans-unsaturated fats also contain double bonds, but the hydrogens are on opposite sides of the double bond, causing the carbon chain to remain straight.
      (26 votes)
  • leaf green style avatar for user Ryan
    So which is healthier, margarine or butter? Margarine is made of hydrogenated vegetable oils, which creates transfats ( starts the section on transfats). Butter is made of animal fat and contains saturated fats.
    (2 votes)
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    • ohnoes default style avatar for user KD
      Margarines are often mistakenly associated with trans fats because they used to be the biggest source pre-90s. However it became known that they're not good for our health so manufacturers found the technology to make margarine without hydrogenation which is the process that creates trans fats. Now it's processed and take-away foods (chips, doughnuts, pies etc) that are the real problem.
      (7 votes)
  • duskpin ultimate style avatar for user Marcos Domínguez
    I didn't get how throwing a bunch of hydrogens into the unsaturated fat turns cis-double bonds into trans-double bonds. Whats the logic behind that?
    (3 votes)
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    • female robot grace style avatar for user tyersome
      Good question!

      Apparently the reaction mechanism involves adding one hydrogen at a time in a reversible reaction and most of the double bonds remaining after the partial hydrogenation will have had a hydrogen added and then lost.

      Since the trans configuration is lower energy than the cis this means that when the double bonds are reformed they usually are converted to the trans configuration.

      You can start to learn more about this here:
      https://en.wikipedia.org/wiki/Trans_fat#Chemistry
      (7 votes)
  • blobby green style avatar for user anushabenny24
    my teacher said that saturated fats are harder for our body to break down... why is that?
    (3 votes)
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  • marcimus pink style avatar for user Eiman Tahir
    So saturated fats are bad for you. But why? They don't have double bonds and double bonds aren't easily broken, right? What is it about the single Carbon-Hydrogen bonds which make saturated fats harmful even when double bonds in unsaturated fats require more energy to be broken down when compared to single bonds? Isn't the whole idea of fats being harmful to your body based on the fact that they aren't easily digested?
    (3 votes)
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    • male robot hal style avatar for user Terence
      unsaturated fats are easier to twist up, because of the double bonds, making it easier for the enzymes to break it down compared to saturated fats that have single bonds, which stack easier, making it hard for enzymes to break it down
      (5 votes)
  • primosaur ultimate style avatar for user nickeldime88
    Which fats are harmful and which fats are helpful to the human body?
    (3 votes)
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  • duskpin tree style avatar for user m pe
    what is this R' (R prime )Sal refers to? I searched the site but found stuff about prime numbers,which I don't think is related,is it?
    (2 votes)
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  • blobby green style avatar for user Nandhini A
    What is PUFA?And why is it healthy?
    (2 votes)
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    • female robot grace style avatar for user tyersome
      Polyunsaturated fatty acids — i.e. fatty acids with more than one double bond.

      Many PUFAs are essential (required in our diet) and they have multiple roles in our metabolism. Several of them (particularly the omega-3 [ω-3] fatty acids) are known to be converted into molecules that have anti-inflammatory properties. However, other PUFAs (especially some of the ω-6 fatty acids) can be converted into molecules that promote inflammation.

      There is ongoing research into many of the PUFA, but there is also a lot of very simplistic or even completely unsupported "nutritional" information going around.

      One thing that does seem relatively clear is that a "westerized" diet high in animal products and saturated fats has negative health outcomes for many individuals.

      The wikipedia articles on fatty acids seem like a decent place to begin learning more:
      https://en.wikipedia.org/wiki/Polyunsaturated_fatty_acid
      https://en.wikipedia.org/wiki/Essential_fatty_acid_interactions
      (4 votes)
  • duskpin ultimate style avatar for user Zoe LeVell
    Why do carbons have to have four covalent bonds at all times? Is it possible for them to have three or five? What controls excess or lesser bonding?
    (3 votes)
    Default Khan Academy avatar avatar for user

Video transcript

- 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.