In this video, we're going to begin our lesson on lipids. And so lipids are actually a very interesting class of molecule because they're actually really, really highly diverse in both their structure and their function. And so it makes it a little bit tougher to organize the lipids because they're so different in their structure and their function. However, one thing that all lipids have in common is that all lipids are hydrophobic biomolecules, and that means that they're going to be insoluble in water, meaning that they will not mix well with water because they are hydrophobic or water fearing. Now although all lipids are hydrophobic, sometimes lipids can also be what's known as amphipathic, And amphipathic is just a fancy word that means that they have both hydrophobic groups that are water fearing and hydrophilic groups that are water loving within the same molecule. And we'll be able to see examples of amphipathic molecules as we move forward in our course. But it's important to keep in mind that although they are all hydrophobic, sometimes they can be amphipathic, having hydrophobic and hydrophilic groups. Now lipids are also a really interesting category of molecule because they're unlike all of the other classes of biomolecules, which are carbohydrates, proteins, and nucleic acids. And that's because carbohydrates, proteins, and nucleic acids, they all use consistent monomers to build polymers. However, the lipids do not have a consistent monomer and so they do not form long chains of polymers like, the other biomolecules do. And so, they are unlike the other classes of biomolecules and they don't form long chains like what we saw in our previous videos. Now once again, there are, lots of different types and classes of lipids, and so we're not going to talk about all of the different types and classes of lipids, but we are gonna talk about some of them, and so, lipids include fats and oils, phospholipids, steroids, and waxes. And so notice down below in our image, we're showing you some of the types of lipids. And so here notice that we have a picture of some butter and some vegetable oil here, perhaps some olive oil. And so this represents the fats and oils, and fats and oils are important for long term energy storage in animals and in plants. And we'll get to talk a lot more about fats and oils as we move forward in our course. So this is just a brief introduction to them. Now the second type that we have here are the phospholipids, which look a little bit like what we see over here. Each individual, one of these structures is a phospholipid, and so they're a major component of cell membranes. And so we'll get to talk a lot more about phospholipids and cell membranes as we move forward in our course, but they are a type of lipid. And then over here in the corner, what we have is an interesting looking structure which represents a steroid. And so, a steroid, is steroids are gonna be an important component of plasma membranes as well. We'll get to talk about cholesterol and how that's an example of a steroid. Moving forward in our course, we'll be able to talk about that. And then steroids can also function as hormones. For example, testosterone and estrogen you may have heard of before, those are examples of steroids and examples of lipids for that matter. And again, we'll get to talk more about these as we move forward in our course. And then the last type of lipid that we're gonna be talking about moving forward in our course are the waxes. And so, the waxes, are going to serve, in the protection and prevention of water loss. An example of a wax is like beeswax, for instance. And so, once again we'll get to talk more about them as we move forward in our course. But for now, this concludes our introduction to lipids and some of the different types of lipids, and I'll see you all in our next video.
2
concept
Fatty Acids
Video duration:
6m
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Video transcript
In this video, we're going to introduce fatty acids. And so, fatty acids are defined as hydrocarbon chains of varying length with a carboxylic acid functional group at the very end. And so we'll be able to see some examples of fatty acids down below when we get to our image. Now really there are 2 main types of fatty acids that you all should know, And the first main type are the saturated fatty acids, which as their name implies with the saturated, these are fully saturated with hydrogens, hydrogen atoms. And so this is because they only contain carbon to carbon single bonds. And when they contain only carbon to carbon single bonds, that means that they can be fully saturated with hydrogens. Now saturated fatty acids tend to be solids at room temperature. And so let's take a look at our example down below at the saturated fatty acids, which we have over here on the far left hand side. So these are saturated fatty acids, because notice that the hydrocarbon chain that we have here, which is only made up of hydrogens and carbon atoms, they're fully saturated with hydrogens. They have the maximum amount of hydrogens on them, because notice that the carbon carbon bonds in here only contain single bonds as we mentioned up above. And so, notice that, this hydrocarbon chain here at the very end, it has a carboxylic acid group which was right here. It's basically a carboxyl group. And so that is why this is a fatty acid, and it's saturated once again because the hydrocarbon chain is fully saturated with hydrogens. Now notice that over here, this is another way to represent the hydrocarbon chain where each of these corners that you see here, each of these points represents a carbon atom, and notice that the hydrogen atoms aren't being shown. It's just another representation, of the same exact molecule. That's why we have the equal sign in between them. Now once again, saturated fatty acids, they tend to be solids at room temperature just like this butter up here. Butter, is of course solid at room temperature, and so that is a source of saturated fatty acids. Now the second main type of fatty acids that you all should know are the unsaturated fatty acids. And so the unsaturated fatty acids, as their name implies, are not fully saturated with hydrogens. And the reason that they're not fully saturated with hydrogens is because they have the presence of at least 1 greater than or equal to 1 carbon to carbon double bond. And so the double bonds that are in the hydrocarbon chain, they create a bend in the chain or a kink in the chain, and the kink in the chain ultimately makes these unsaturated fatty acids liquids at room temperature instead of being solids at room temperature. And so when we take a look at our image down below over here in the middle, notice what we're showing you is an example of unsaturated fatty acids, and notice that the hydrocarbon chain that we have here is not fully saturated with hydrogens because there is a carbon to carbon double bond. And so there is, they are missing some hydrogens here at these positions. And so that's why they call them unsaturated because they're not fully saturated due to the presence of a double bond. Now notice that the double bond also creates a bend in the chain. It's not straight or linear like the saturated fatty acids are. It creates a bend or a kink in the chain. And so because it has a kink in the chain, the unsaturated fatty acids, they cannot be tightly packed together, so they're gonna remain relatively loose. And that loose nature is why they are liquids at room temperature. So these oils, vegetable oils and olive oil and things like that, they are examples of unsaturated fatty acids that are liquids at room temperature. Now there is one subset of unsaturated fatty acids that are called trans fatty acids. And so you may have heard of trans fatty acids or trans fats before, and really these are a subtype of unsaturated fatty acids. That's why we have them grouped in the same, grouping as unsaturated fatty acids. So trans fats are artificial unsaturated fatty acids. And instead of having a kink, the the trans fats, they actually do not have a kink in their chain. So they have a double bond, but the double bond does not make them kinked, and so they remain linear. So let's take a look at the trans fatty acid, which we have down below right here. And so notice that the trans fatty acid, does have a double bond in its chain. However, notice that the double bond that's in the chain of the trans fatty acid does not create a kink in the chain or a bend in the chain like, other unsaturated fatty acids. Trans fatty acids specifically are going to have straight, chains despite having a double bond in them. Now trans fatty acids, again, they are, artificially made, and so you'll find them in foods like, burgers and french fries and, things of that nature. And so that's why we have this image right here. And trans fatty acids usually they're associated with being very unhealthy. And so, this is, typically types of foods that you would want to try to avoid in your typical everyday diet. And so this here concludes our introduction to fatty acids and, the difference between saturated and unsaturated fatty acids. And we'll be able to get some practice moving forward in our course. So I'll see you all in our next video.
3
Problem
Problem
Which type of fatty acids only contain Carbon-Carbon single bonds?
a) Unsaturated.
b) Saturated.
c) Trans fats.
d) Steroids.
A
Unsaturated.
B
Saturated.
C
Trans fats.
D
Steroids.
4
concept
Triglycerides
Video duration:
3m
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Video transcript
So now that we know what fatty acids are, in this video, we're going to talk about how fatty acids can be used to build another type of lipid called Triglycerides. And so Triglycerides, as their name implies with the tri prefix here, these are lipids with 3 fatty acid chains. And so the tri- is a prefix that means 3, and that's why they have 3 fatty acid chains. Now these 3 fatty acid chains in a triglyceride are going to be covalently linked to a single glycerol molecule. Now fatty acids are going to be linked to the glycerol molecule via dehydration synthesis reactions. And so we know that dehydration synthesis reactions are used to build up a molecule. So let's take a look at our image down below to get a better understanding of this triglyceride. So notice over here on the far left what we're showing you is a molecule in purple that represents the glycerol molecule, the single glycerol molecule we were discussing up above here. And then also notice over here in yellow, we have these 3 fatty acids, and so we can go ahead and put 3 fatty acids here. And so notice that the fatty acids are all separate from one another here in this image and the glycerol is also separate. And so if we want to combine these separate units together and build a larger structure, then of course we're going to need a dehydration synthesis reaction. And so notice that each of these chains, these fatty acid chains here, can undergo a dehydration synthesis reaction to release 3 water molecules, one for each of the chains that interacts with each of these, components here on the glycerol. And so you can see the Ohs here, that react with the Hs here to form, water molecules, and there are 3 of them that get formed. And once again, that's why we have the 3 out in front. Now notice over here on the far right, after the dehydration synthesis reactions, we've now combined and connected these, 3 fatty acids covalently to the glycerol molecule. And so, recall that when we have 3 fatty acid chains covalently linked to a single glycerol molecule, we've then created a tri Triglyceride. And so over here on the right, we have the Triglyceride. Now, of course, if we wanted to break down the triglyceride into, its separate components like what we see over here, then of course we're going to need the hydrolysis reaction. And so the hydrolysis reaction, is of course going to use water to break apart the Triglyceride into its smaller components. And Triglycerides are going to be a main source of fats. This is how fats are stored in animal cells and, the fats that we have are stored as triglycerides. And so this here concludes our introduction to triglycerides. And once again, we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.
5
Problem
Problem
A triglyceride is a form of _______ composed of ___________.
a) Lipid ; fatty acids & Glucose.
b) Lipid ; Fatty acids & Glycerol.
c) Carbohydrate ; Fatty acids only.
d) Lipid ; Ribose.
A
Lipid ; fatty acids & Glucose.
B
Lipid ; Fatty acids & Glycerol.
C
Carbohydrate ; Fatty acids only.
D
Lipid ; Ribose.
6
concept
Phospholipids
Video duration:
4m
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Video transcript
In this video, we're going to introduce yet another type of lipid called the phospholipid. And so phospholipids as their name implies are lipids themselves. In fact, they are a large class of lipids. And also as their name implies with the phospho here, these are a large class of lipids that contain a phosphate group, which recall is one of the functional groups that you all should be familiar with. And so phospholipids are actually a major component of all cell membranes, and we'll be able to see this down below in our image. Now later in our course we'll talk more details about cell membranes, but in this video we're focusing specifically on phospholipids. Now phospholipids are what we call amphipathic molecules, And amphipathic, recall, is just a fancy word that means that it contains both hydrophilic or water loving and hydrophobic or water fearing groups. And so phospholipids are amphipathic molecules with a hydrophilic head and a hydrophobic tail. Hydrophobic tails, I should say. And so if we take a look at our image down below at these phospholipids, notice that on the far left we're showing you a cell, and we're zooming in specifically to the cell's membrane, which is, this, little area that's right here. And when we zoom into the cell's membrane, what we'll see is that the vast majority of the membrane is made up of these little structures, these little units that we see here that we call phospholipids. And so if we zoom into just one of these units, and blow it up, it would look like what we see right here. And so it noticed that it really has two regions. It has this head region that's up here, and then it has the two tails that extend down below. And so the head region is a hydrophilic region, a hydrophilic head. So this is the head. And, that means that it is water loving and interacts with water. Whereas the two tails that we see down below, these are hydrophobic tails, meaning that they are water fearing. And so, these tails that we see here are trying to get away from water. And so because we have a single molecule here with both hydrophilic groups and hydrophobic groups. That is why we call this an amphipathic molecule. Now if we were to zoom into the structure of the phospholipid even more, we could see the details of its chemical structure, which we see over here. And so notice that it does contain, fatty acids, which are these yellow regions here. It also will have glycerol molecule, and then it will also have a phosphate molecule at the top. And so this phosphate functional group is why we call them phospholipids. And so, really this here concludes our introduction to phospholipids and we'll be able to talk more about phospholipids later in our course when we're talking about cell membranes. But for now, this here concludes our introduction to phospholipids and we'll be able to get some practice as we move forward in our course. So I'll see you all in our next video.
7
Problem
Problem
How do phospholipids interact with water molecules?
a) The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract).
b) Phospholipids do not interact with water because water is polar and lipids are nonpolar.
c) The polar heads interact with water; the nonpolar tails do not.
d) Phospholipids dissolve in water.
A
The polar heads avoid water; the nonpolar tails attract water (because water is polar and opposites attract).
B
Phospholipids do not interact with water because water is polar and lipids are nonpolar.
C
The polar heads interact with water; the nonpolar tails do not.
D
Phospholipids dissolve in water.
8
concept
Steroids & Waxes
Video duration:
3m
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Video transcript
In this video we're going to introduce 2 other classes of lipids, the steroids and waxes. And so steroids are a complex class of lipids that look very different from the other lipids that we've talked about so far in our course And this is because the steroids are not made of fatty acids. Instead, these steroids are going to be lipids that are made of 4 fused carbon ring structures. Now, the molecule cholesterol is actually a classic example of a steroid. And you may have heard of this molecule cholesterol before because cholesterol is a common steroid that is important for the structure of animal cell membranes. And so if we take a look at our example image down below, notice that this molecule we're showing you right here on the left is cholesterol which again is a classic example of a steroid. Now, again, steroids have 4 fused carbon ring structures and notice that each of the 4 fused carbon ring structures are numbered in this cholesterol molecule down below 1, 2, 3, and 4. Now again, cholesterol is critical to the structure of animal cell membranes and so on the right side of the image notice we're showing you an animal cell membrane which we know from our previous lesson videos that cell membranes are predominantly going to be made of these phospholipid molecules and so you can see these phospholipids here in this membrane. However, embedded, in between this phospholipid bilayer you'll find these cholesterol molecules in animal cell membranes. And so, later in our course we'll get to talk more about the exact role of cholesterol in the cell membrane but for now, you should just note that steroids are another class of lipid and cholesterol is an example of a steroid. Now, the waxes again are a second class of lipid and they are going to be predominantly used for protection purposes as well as the prevention of water loss. And so notice over here on the right side of our image what we're showing you is a structure of a molecule that represents a wax. And so, this molecule right here is actually a structure that makes up beeswax and so that's why we are showing you a bee over here And so notice that this wax molecule is going to be made up of a fatty acid and so you can see the fatty acid is right here and it is also going to be made up of a long chain, a molecule that used to be a long chain alcohol group and so at this end right here this used to be an alcohol group with a hydroxyl group there. But after combining to this fatty acid that alcohol group is no longer there. But this here concludes our brief lesson on steroids and waxes, these other two classes of lipids, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
9
Problem
Problem
The molecule shown the figure is a ________.
a) Fatty acid.
b) Wax.
c) Steroid.
d) Triacylglycerol.
e) Phospholipid.
A
Fatty acid.
B
Wax.
C
Steroid.
D
Triacylglycerol.
E
Phospholipid.
10
Problem
Problem
Choose the correct statement about biological waxes:
a) They contain at least one steroid molecule.
b) They are fatty acids bound to long chain alcohol molecules.
c) They are extremely hydrophilic.
d) They are made of 4 fused carbon ring molecules.
A
They contain at least one steroid molecule.
B
They are fatty acids bound to long chain alcohol molecules.