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Sphingolipids – Lipids

by Kevin Ahern, PhD
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    00:00 that's where all the fatty acids are residing and that's where it will be very, very nonpolar.

    00:01 Now another component of the lipid bilayer are molecules that we call sphingolipids and these sphingolipids also have a dual character associated with it. Now what you see on the screen here is a general class of sphingolipids molecules called ceramides. A ceramide has a structure such as you see here. At first glance it looks a little bit like a diacylglycerol, or it looks a little bit like the phospholipids that we've seen before, it doesn't have the phosphate yet. So for example we see a long chain fatty acid projecting off to the left in green and we see a long chain nonpolar molecule called sphingosine which is projecting off to the left in orange. On the right side we have the basics of what was a backbone of the glycerol compound, not the same structure as glycerol but resembling glycerol certainly.

    00:48 Last we see an R group there and it's the R group attachment that gives rise to the specific type of sphingolipids that we're talking about. So for example, if R is equal to phosphocholine, then we've just created a molecule known as sphingomyelin. Sphingomyelin is a very, very important component of the myelin sheath of nerve cells. If R is a simple sugar or a single sugar, then that resulting sphingolipid is called a cerebroside. And if R is a complex oligosaccharide, then we've created a sphingolipid known as a ganglioside.

    01:27 Now we can see these molecules here for example. Here's sphingomyelin and we can see that sphingomyelin has a very hydrophilic head, as shown on the right and a very hydrophobic tail. So even though the sphingolipids have a structure that's slightly different from the glycerolphospholipids, they have the same chemical nature as the glycerolphospholipids and they also are components of membranes and the lipid bilayer that we saw previously.

    01:54 Here is a structure of a cerebroside and a cerebroside contains a simple sugar, in this case glucose that's been linked to the ceramide backbone. When you link a glucose or a single sugar to a ceramide backbone, you create a cerebroside. There is the hydrophilic head and because glucose has a lot of hydroxyl groups with it, it can associate very well with water, whereas the rest of the sphingolipid has the hydrophilic tail that we've seen before and will not associate with water.

    02:22 This depicts a ganglioside and a ganglioside of course is a sphingolipid that contains a complex carbohydrate linked to it. This too, has a very polar part that's up at the top on the right, as you can see here in green and a very nonpolar part, the hydrophobic tail that is shown on the left.


    About the Lecture

    The lecture Sphingolipids – Lipids by Kevin Ahern, PhD is from the course Biochemistry: Basics.


    Included Quiz Questions

    1. Sphingomyelin
    2. Cerebroside
    3. Ganglioside
    4. Diacylglycerol
    5. Sphingosine
    1. Sphingomyelin — glucose
    2. Ganglioside — palmitoyl-CoA
    3. Cerebroside — simple sugar
    4. Ganglioside — complex oligosaccharide
    5. Sphingomyelin — phosphocholine

    Author of lecture Sphingolipids – Lipids

     Kevin Ahern, PhD

    Kevin Ahern, PhD


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