Sphingolipids: Study with Video Lessons, Practice Problems & Examples

Sphingolipids are a class of lipids that utilize sphingosine, an 18-carbon amino alcohol, as their backbone instead of glycerol. They contain one variable fatty acid linked via an amide bond, distinguishing them from glycerolipids, which have two fatty acids linked by ester bonds. Sphingolipids are crucial components of eukaryotic cell membranes, second only to glycerolipids. The presence of different variable head groups, attached through phosphodiester or glycosidic linkages, leads to various classes of sphingolipids, including ceramides, which have a hydrogen atom as their head group.

Sphingolipids

In this video, we're going to begin our lesson on sphingolipids. Now, before we actually define sphingolipids, let's first revisit our lipid map to make sure everyone's on the same page. And so we know that right now we're currently exploring all of the fatty acid based lipids. And so far in our previous lesson videos, we've already covered glycerolipids including triacylglycerols and Glycerophospholipids. And we also talked about different classes of Glycerophospholipids as well including the class that does not have a variable head group, the phosphatidates, and then we also talked about the other classes of Glycerophospholipids that have these head groups that we see down below. And we know that all of these glycerophospholipids here are indeed phospholipids that have a glycerol molecule as the platform. But there are also phospholipids that don't use glycerol as the platform and these would be, that's why we have platform 2 over here. And so now that we've explored the entire Glycero lipids to its end, we're going to zoom out and start our next class of fatty acid based lipids. And these are again the sphingolipids. And, so, just like glycerolipids use a glycerol molecule as the platform, sphingolipids use a sphingosine molecule as the platform. And so in our next lesson video, we'll introduce that sphingosine molecule. And then after we introduce the sphingosine molecule, you can see the direction that we're going to head in. We're going to explain the phospholipid that uses platform number 2 and then we'll also explain this other sphingolipid type over here as well. And so I'll see you guys in our next lesson video when we explain the sphingosine molecule. So see you guys there.

Sphingolipids

In this video, we're going to introduce the sphingosine molecule, and sphingosine is an unsaturated 18 carbon amino alcohol group. By amino alcohol, it means that it has both an amino group and alcohol groups as well. If we take a look down below at the structure of sphingosine, what we'll note is that it indeed has a total of 18 carbon atoms. It also has an amino group right here at this position, and it has an alcohol group over here at this position. That's exactly how we defined it above. Also, note that sphingosine actually has a trans double bond, which is unique because recall that most unsaturated fatty acids have cis double bonds. But sphingosine specifically has a trans double bond, so that is definitely worth noting. Notice that the double bond over here is actually in the trans configuration, going on opposite sides of the double bond.

Another thing to note is that sphingosine's structure is actually derived from the fatty acid palmitate and a serine amino acid. Notice down below we have this portion here, that is specifically from the Serine molecule. You can see that the amino group is coming from Serine's structure and then notice that this portion down here is coming specifically from the fatty acid Palmitate. Because it is derived from a fatty acid Palmitate, that means that sphingosine is a fatty acid-based molecule. Notice specifically we have carbons 1, 2, and 3 numbered here for sphingosine's structure, and sphingosine's carbons 1, 2, and 3 are actually structurally analogous to glycerol's carbons in Glycerophospholipids. You can see that at these positions, there's the possibility for a fatty acid to be attached here at the C2 carbon, and there's also the possibility for a variable head group to be attached here at the C1 carbon. You can see how this has somewhat of a resemblance to glycerol's carbon atoms. Again, the variable head group X in sphingosine can be modified to contain different variable head groups, just like Glycerophospholipids can be modified to obtain different variable head groups. Specifically, in sphingosine's structure, this variable head group here is actually going to be a hydrogen atom in sphingosine, so this X here would actually be a hydrogen atom, again in sphingosine's actual structure.

One thing to note here about sphingosine is that it actually sounds like "springosine". If you think about a spring here and compare it to sphingosine's structure, you'll kind of notice somewhat of a resemblance. So, this part right here that extends out from the backbone somewhat resembles the spring and then, of course, this portion up here would be this portion here. If you're able to remember, sphingosine is kind of like "springosine", then hopefully that'll also help you remember the shape and function of sphingosine. Now that we've introduced sphingosine, in our next lesson video, we'll be able to put all this together and talk more details about sphingolipids. I'll see you guys in that next video.

Sphingolipids

Alright. So now that we've introduced the molecule sphingosine, in this video, we're going to revisit sphingolipids. Sphingolipids, as the name implies, are just lipids that contain a sphingosine molecule or one of sphingosine's derivatives, and it contains this sphingosine molecule instead of containing a glycerol molecule like what glycerolipids have. One thing that's very important to note about sphingolipids is that they actually only have one variable fatty acid that is attached to the sphingosine. If you take a look at the image down below, notice that we have this variable fatty acid shown here in yellow, and so we can go ahead and label this as a variable fatty acid. You might be thinking, hey, isn't this over here a fatty acid too? Didn't we say that it was derived from the fatty acid palmitate in our last lesson video? And I would say, yes, you are right. This is a fatty acid. However, it's not a variable fatty acid because this fatty acid here is constant, and it's always going to be in the structure of sphingosine. And so, this fatty acid here is not going to change, and the only variable one is this one here at the C₂ position. That’s a big difference from glycerolipids because recall glycerolipids actually have two variable fatty acids, whereas sphingolipids again only have one variable fatty acid. Another big difference is that this one variable fatty acid is linked via an amide linkage. You can see that this variable fatty acid is linked right here at this position, via an amide linkage. This is critical in the structure of sphingolipids, and also recall that in glycerolipids, the fatty acids are not linked via amide linkages, instead, they're linked via ester linkages. This is definitely a unique feature that you should know, the amide linkage here. Sphingolipids are the second most abundant lipids in eukaryotic cell membranes, of course behind glycerolipids. If we take a look at our image down below, notice we're zooming into the cell's plasma membrane and notice that most of the cells that we see here, in purple are actually the glycerophospholipids. But scattered throughout there are other types of lipids like these blue ones, and that's the one that we're zooming into over here, the sphingolipids. You can find sphingolipids in the plasma membrane, but they are going to be the second most abundant. And as we mentioned in our last lesson video, the variable head group here, can have different chemical groups, and that's going to create different classes of sphingolipids that we'll talk about later in our course. These variable head groups can either be attached via a phosphodiester linkage or they could be attached via a glycosidic linkage. This is what's going to lead to the two different classes of sphingolipids that again we'll talk about moving forward in our course. The last thing that you should note here is that specifically because there is an amide linkage linking this variable fatty acid, that, as soon as this amide linkage is created, this molecule is referred to as ceramide, and you can see the word 'amide' in there indicating that the amide linkage is present. A ceramide molecule is one where this variable head group here is just a hydrogen atom. There's no head group there; it's just the hydrogen. And so that's important to keep in mind as well. This here concludes our introduction to sphingolipids, and we'll be able to get some practice applying all of these concepts in our next couple of videos. So I'll see you guys there.

Which component is found in all sphingolipids?

A) A carbohydrate.

B) A negative charge.

C) A phosphate group.

D) An amino alcohol.

E) All the above are found in all sphingolipids. 

F) None are found in sphingolipids.

• A. A carbohydrate.
• B. A negative charge.
• C. A phosphate group.
• D. An amino alcohol.
• E. All the above are found in all sphingolipids.
• F. None are found in sphingolipids.

Which of the following is true about sphingolipids?

A) They are all phospholipids.

B) They all contain a carbohydrate backbone.

C) They can have either a phosphodiester or a glycosidic linkage to their polar head group.

D) The all contain a glycerol molecule backbone. 

E) None of the above are true.

• A. They are all phospholipids.
• B. They all contain a carbohydrate backbone.
• C. They can have either a phosphodiester or a glycosidic linkage to their polar head group.
• D. The all contain a glycerol molecule backbone.
• E. None of the above are true.

Here’s what students ask on this topic:

What are sphingolipids and how do they differ from glycerolipids?

Sphingolipids are a class of lipids that use sphingosine, an 18-carbon amino alcohol, as their backbone instead of glycerol. They contain one variable fatty acid linked via an amide bond, distinguishing them from glycerolipids, which have two fatty acids linked by ester bonds. Sphingolipids are crucial components of eukaryotic cell membranes, second only to glycerolipids. The presence of different variable head groups, attached through phosphodiester or glycosidic linkages, leads to various classes of sphingolipids, including ceramides, which have a hydrogen atom as their head group.

What is the structure of sphingosine and how is it derived?

Sphingosine is an unsaturated 18-carbon amino alcohol. It has an amino group and an alcohol group, with a unique trans double bond. The structure of sphingosine is derived from the fatty acid palmitate and the amino acid serine. Specifically, the amino group comes from serine, while the rest of the structure is derived from palmitate. This makes sphingosine a fatty acid-based molecule. The carbons 1, 2, and 3 of sphingosine are structurally analogous to the carbons in glycerol, allowing for the attachment of a variable fatty acid and a variable head group.

What are the different classes of sphingolipids?

The different classes of sphingolipids are determined by the variable head groups attached to the sphingosine backbone. These head groups can be attached via phosphodiester or glycosidic linkages. The main classes include ceramides, which have a hydrogen atom as their head group, and other sphingolipids with more complex head groups. The specific head group determines the function and classification of the sphingolipid. For example, sphingomyelins have a phosphocholine or phosphoethanolamine head group, while glycosphingolipids have sugar moieties as their head groups.

What role do sphingolipids play in cell membranes?

Sphingolipids are essential components of eukaryotic cell membranes, where they contribute to membrane structure and function. They are the second most abundant lipids in these membranes, after glycerolipids. Sphingolipids help in forming lipid rafts, which are specialized membrane microdomains involved in cell signaling, protein sorting, and membrane fluidity. The unique properties of sphingolipids, such as their ability to form tight, ordered structures, make them crucial for maintaining the integrity and functionality of cell membranes.

What is a ceramide and how is it related to sphingolipids?

A ceramide is a type of sphingolipid where the variable head group is a hydrogen atom. It consists of a sphingosine backbone with a single fatty acid attached via an amide bond. Ceramides are fundamental building blocks for more complex sphingolipids. They play a critical role in cell membrane structure and function, as well as in signaling pathways related to cell growth, differentiation, and apoptosis. The presence of the amide linkage in ceramides is a key feature that distinguishes them from other lipid types.