Sphingomyelins: Study with Video Lessons, Practice Problems & Examples

Sphingolipids are unique lipids characterized by a sphingosine backbone, an 18-carbon amino alcohol. Sphingomyelins, a type of phospholipid, consist of a sphingosine backbone, one fatty acid, a phosphate group, and a choline head. The amide bond links the fatty acid to the sphingosine. Sphingomyelins are crucial for forming the myelin sheath, which insulates nerve fibers, enhancing signal transmission. Understanding these structures is essential for grasping cellular membrane dynamics and neurological function.

Sphingomyelins Concept 1

Now before we can talk about sphingomyelins, we first need to talk about sphingolipids. These are lipids that have a sphingosine backbone. We're going to say a sphingosine itself is an 18-carbon amino alcohol. Some key characteristics of a sphingosine are, carbons 1-3 are analogous to glycerol. Here, you'll notice that, typically when we talk about other types of fatty acids, we usually number from 1 down to 3. Here, it's kind of inverted on its head. So one starts here on the bottom, and it moves up to 3. We're going to say carbons 1-3 are analogous to glycerol, so they have OH groups on those carbons. Next, we're going to say our amino group, which is NH₂, is at carbon number 2, so there's an NH₂ here. Then we're going to say 15 carbons are attached to carbon 3. So we have this long chain that extends to 15 carbons, because remember it's 18 carbons. We have 1 to 3 here, and then the other 15. And then finally, we're going to say we have a trans double bond at carbon number 4. With this information, that's how we're able to create this image of a typical sphingosine. So just remember, we're talking about sphingolipids. These are lipids that have a sphingosine backbone. Sphingosine itself has these characteristics that make it unique.

Sphingomyelins Concept 2

Now, sphingomyelins are phospholipids with a sphingosine backbone and one fatty acid. Here, we're going to say phosphate and a choline head group form the head of the structure. We're going to say one tail is the sphingosine chain, and the other tail is a fatty acid attached to an amide bond. If we take a look here at our chart, again, we're dealing with fatty acids. We're going to come down where we're dealing with our sphingomyelin. And we're going to say here, if we take a look at our sphingomyelin, we're going to say we have our sphingosine backbone here, which is this part here. We're going to say that we have on carbon number 1, this phosphate group. Remember we're dealing with a choline head, so that means that the oxygen of the phosphate group is connected to an ethyl. And remember choline CH means that we have a nitrogen connected to CH₃, 3 of them, because nitrogen makes 4 bonds, it's positively charged. And then remember we're making an Amide Bond here on carbon number 2. So remember, an amide is where we have a carbonyl group connected directly to a nitrogen. Now, here we're going to say this is important, that sphingomyelins are primary structural components of the myelin sheath. So, this is what we're talking about: nerve fiber coating. We'll talk about later on in terms of the myelin sheath when we talk about muscles. So, for right now, just keep that in mind. Alright. And these are the characteristics of a typical sphingomyelin structure.

Sphingomyelins Example 1

For this example question, it asks, which one of the following statements about sphingomyelins is incorrect? Here, the fatty acid at carbon 2 is attached through an amide linkage. That there is true, so this can't be an answer. The backbone molecule in sphingomyelins is sphingosine. That is also true. It's not glycerol like we've seen in other molecules; it's sphingosine. Sphingomyelins are essential for the structural integrity of the myelin sheath. This is an important fact when it comes to our sphingomyelin. So, this is also true. The odd one out is option d. Let's see why that is. A sphingomyelin has only one tail because it contains one fatty acid. So here, we have a fatty acid chain at carbon number 2, but it has more than one tail. It has also a hydrocarbon tail at carbon number 3, but we have also the presence of that trans double bond. Hence, this statement is incorrect. Here, the answer would be option d. This is the only incorrect statement out of the 4 given to us.

Sphingomyelins Example 2

In this video, we're going to talk about drawing sphingomyelins. So, drawing sphingomyelin requires recalling the structures of sphingosine and the fatty acids involved. Now, here it says, draw the structure of a sphingomyelin that contains oleic acid. Remember, oleic acid represents an unsaturated fatty acid. Its standard notation or shorthand notation is 18:1. Meaning that we have an 18 carbon fatty acid chain, 1 means we have 1 pi bond, and with these unsaturated fatty acids with 1 pi bond, it's typically at carbon number 9 where we first see it.

Now, come down here, we're going to say step 1 is to draw the sphingosine backbone with a phosphate group at carbon number 1. So here goes carbon number 1 and there's a phosphate group there. We're going to say instead of an NH₂ group at carbon number 2, we're going to write only NH. So here there's going to be an NH group right here. And that's because we're going to attach something to that NH group.

Step 2, we're going to extend the phosphate at carbon number 1 with the choline head group. Remember, we're not saying choline, but co-choline head group. So, in choline, we have an ethyl group attached to the oxygen, and then we have nitrogen. Choline is CH. Nitrogen is connected to CH₃, 3 of them. Because it's making 4 bonds, it's positively charged.

Coming down to step 3, we're going to draw the fatty acyl group, so the fatty acid without the OH, from the NH group at carbon number 2. So here goes our amide linkage or amide bond that's going to be formed. So, remember, oleic acid is an unsaturated fatty acid. Its standard or shorthand notation is 18:1. So we have 18 carbons, so we have 2, 4, 6, 8, 10, 12, 14, 16, 18, just to be sure. This would be the structure of our sphingomyelin based on the information given to us within the example question. We have our amide bond on Carbon number 2 in terms of its NH group. We have our Phosphate group, as well as the Choline head group on carbon number 1. And of course, on carbon number 3, we have our 15 carbon chain that's also containing a trans double bond.

Alright, so this would be our final answer.

Draw a sphingomyelin that contains palmitoleic acid.

• A.
• B.
• C.
• D.

Which one of the following statements describes how sphingomyelins are similar to glycerophospholipids?

• A. Sphingomyelins have the same number of fatty acids as glycerophospholipids.
• B. Sphingomyelins and glycerophospholipids have the same linkage that holds the fatty acids.
• C. Sphingomyelins and glycerophospholipids have phosphate with head groups.
• D. Both can be classified as sphingolipids.

Which one of the following statements is incorrect about triacylglycerols and phospholipids?

• A. Triacylglycerols contain glycerol while phospholipids do not.
• B. Phospholipids have a phosphate group attached at C3.
• C. Phospholipids and triacylglycerols contain 2 and 3 fatty acids, respectively.
• D. Due to polar head groups, phospholipids have a higher water solubility than triacylglycerols.

Here’s what students ask on this topic:

What is the structure of sphingomyelins?

Sphingomyelins are phospholipids characterized by a sphingosine backbone, which is an 18-carbon amino alcohol. The structure includes one fatty acid attached via an amide bond, a phosphate group, and a choline head group. The sphingosine chain forms one tail, while the fatty acid forms the other. The phosphate group is connected to the choline head, which consists of a nitrogen atom bonded to three methyl groups (CH₃). This unique structure is crucial for the formation of the myelin sheath, which insulates nerve fibers and enhances signal transmission.

What role do sphingomyelins play in the myelin sheath?

Sphingomyelins are essential components of the myelin sheath, the protective covering that insulates nerve fibers. This insulation is crucial for the efficient transmission of electrical signals along the nerves. The myelin sheath allows for faster signal propagation and prevents signal loss, ensuring proper neurological function. Without sufficient sphingomyelins, the integrity of the myelin sheath would be compromised, leading to potential neurological disorders.

How do sphingomyelins differ from other phospholipids?

Sphingomyelins differ from other phospholipids primarily in their backbone structure. While most phospholipids have a glycerol backbone, sphingomyelins have a sphingosine backbone, an 18-carbon amino alcohol. Additionally, sphingomyelins have one fatty acid attached via an amide bond, whereas other phospholipids typically have two fatty acids attached via ester bonds. The presence of a choline head group and a phosphate group further distinguishes sphingomyelins from other phospholipids.

What is the significance of the amide bond in sphingomyelins?

The amide bond in sphingomyelins is significant because it links the fatty acid to the sphingosine backbone. This bond is formed between the carbonyl group of the fatty acid and the amino group of the sphingosine. The amide bond provides structural stability to the sphingomyelin molecule, which is crucial for its role in forming the myelin sheath. This stability ensures that the myelin sheath can effectively insulate nerve fibers and facilitate efficient signal transmission.

What are the key characteristics of sphingosine in sphingolipids?

Sphingosine is an 18-carbon amino alcohol that serves as the backbone for sphingolipids. Key characteristics include: carbons 1 to 3 are analogous to glycerol, with hydroxyl groups (OH) on these carbons; an amino group (NH₂) at carbon 2; a long chain of 15 carbons attached to carbon 3; and a trans double bond at carbon 4. These features make sphingosine unique and essential for the structure and function of sphingolipids, including sphingomyelins.