Types of Lipids (continued)
Sphingolipids
These are somewhat more complex lipids with a superficial resemblance to glycerophospholipids. All of them contain, instead of glycerol, the fatty acid derivative sphingosine
.
Sphingolipids have a fatty acid (sometimes a very long one) attached to the amino group of sphingosine and a compound X attached to the terminal hydroxyl group of sphingosine. Here are some examples:
|
If the X compound is... |
then the sphingolipid is... |
|---|---|
|
H |
ceramide |
|
Phosphocholine |
sphingomyelin |
|
a simple sugar |
a cerebroside or globoside |
|
a complex sugar |
a ganglioside |
Sphingolipids play important roles in certain membranes. They are often involved in signaling. Just like any other biochemical compound, they have to be broken down eventually. Lesions in the degradation pathway of certain sphingolipids can cause very serious diseases such as Tay-Sachs.
Steroids
Structurally steroids have a "sterane" core, consisting of three 6-carbon rings and a 5-carbon ring. The best-known of the steroids is cholesterol.
Cholesterol is an important constituent of our membranes. It is also the starting point for synthesis of the steroid hormones and bile acids. This topic is not covered within this module.
