Lipids (Part 9 of 11) - Membrane Lipids - Sphingolipids

Moof's Medical Biochemistry Video Course: moof-university.thinkific.com/courses/medical-bioc… Questions Answered in This Video: What are sphingolipids, and what is their general structure? Are sphingolipids phospholipids, glycolipids, both, or neither? What is the parent compound of sphingolipids? What are the subclasses of sphingolipids, and where and why are they important? What is a sphingomyelin? What are the neutral glycolipids, and why are they called that? What are cerebrosides and globosides? What are gangliosides? Don't forget to LIKE, COMMENT, and SUBSCRIBE: youtube.com/subscription_center?add_user=MoofUnive… INFORMATION ABOUT TUTORING: www.moofuniversity.com/tutoring/ TO SUPPORT MOOF UNIVERSITY WITH A FINANCIAL CONTRIBUTION: www.moofuniversity.com/support-moof/ INSTAGRAM: instagram.com/moofuniversity/ FACEBOOK: www.facebook.com/pages/Moof-University/15548589347… TWITTER: twitter.com/moofuniversity Video Content Summary: Sphingolipids are primarily characterized by their sphingosine backbone, the first three carbons of which are analogous to the three carbons in glycerol, in terms of their role as the backbone. The rest of the carbons of the sphingosine backbone, in a sense, take the place of where a fatty acid would normally be attached in the case of a glycerol backbone. The second carbon of the sphingosine backbone has a fatty acid linked to it via an amide bond, unlike the ester bond found in glycerolipids. The fatty acyl group attached there is usually a saturated chain or a monounsaturated chain with 16, 18, 22, or 24 carbons. At the first carbon of the sphingosine backbone, we have a polar head group. The identity of the polar head group determines which type of sphingolipid we have. If a phosphate group is attached via a phosphodiester linkage, the sphingolipid is also a phospholipid. If, instead, a carbohydrate portion is attached via a glycosidic linkage, the sphingolipid is also a glycolipid. However, if neither is attached we instead just have an OH group attached, we would have the parent compound of sphingolipids, called ceramide. There are three subclasses of sphingolipids. They are: 1) sphingomyelins, 2) glycosphingolipids, and 3) gangliosides. They all differ based on what is specifically attached as the polar head group. If the polar head group consists of a phosphocholine or phosphoethanolamine, you have a sphingomyelin. Sphingomyelins exist in plasma membranes of animal cells, and they are named specifically because of their prevalence in the myelin sheaths of insulated axons of certain neurons. If the polar head group consists of one or more sugars, you have a glycosphingolipid. Glycosphingolipids are also known as neutral glycolipids because when the polar head group consists only of sugar moieties, no charge results. Glycosphingolipids are further classified into 1) cerebrosides, if the polar head group contains only one sugar and 2) globosides, if the polar head group contains two or more sugars. For cerebrosides, those that contain glucose as the sugar are found in non-neural plasma membranes, while those that contain galactose as the sugar as found in neural plasma membranes. When you combinations of sugars, you, of course, have a globoside. Glycosphingolipids are important in blood typing. If the polar head group consists of sugars AND AT LEAST ONE sialic acid, you have the most complex of the sphingolipids, a ganglioside. So, basically, a ganglioside is a globoside with at least one sialic acid group attached to it, and because gangliosides have these acid groups attached to them, they can be charged. So, in essence, they are charge glycolipids, unlike the neutral glycolipids. Gangliosides are classified into series based on the number of sialic acids contained within them: 1 - GM (mono), 2 - GD (di), 3 - GT (tri), 4 - GQ (quat).

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