6.5: Sphingolipids
- Define and understand the structure of sphingolipids, their subclasses, and their role in the nervous system.
- Understand the role of sphingolipids in multiple sclerosis.
Sphingolipids and their subclasses
Sphingolipids are a class of lipids having a sphingoid base that is a set of aliphatic amino alcohols, including sphingosine, shown in Figure \(\PageIndex{1}\). When the amino (\(\ce{-NH2}\) group is attached to a fatty acid by an amide bond, it is called ceramide . When the primary alcohol of ceramide is linked to a phosphorylcholine or phosphorylethanolamine group, it is called sphingomyelin . When the primary alcohol of ceramide is bound to glucose or galactose by a glycosidic bond, it is called cerebroside . When a glycosidic bond connects the primary alcohol of ceramide to an oligosaccharide with one or more sialic acids, it is called ganglioside .
Figure \(\PageIndex{2}\) illustrates two examples of sphingomyelin. Like glycerophospholipids, these sphingolipids are an essential component of the lipid bilayer. Mainly, they are abundant in the brain and nerves. They are abundant in the white matter of myelin sheath, i.e., a coating surrounding the nerve cells. Myelin sheath increases the speed of nerve impulses and is essential in protecting nerve cells, signal transduction, and cell recognition.
Multiple sclerosis is a nervous system disease in which the myelin sheaths wrapped around axons of nerve cells are damaged, as illustrated in Figure \(\PageIndex{3}\). Symptoms are related to the retardation of signal conduction by the nerves that, in turn, reduces sensation, coordination, movement, cognition, muscle weakness, blindness, and other functions involving nerves. The severity of the effects depends on the amount of damage. Studies indicate that vitamin D may lessen the severity of the disease. Nearly 1 million people in the US and about 2.8 million worldwide have multiple sclerosis.