Answer:
Amide
Explanation:
Sphingomyelin is the most abundant sphingolipid in animal tissues: its presence in all cell membranes studied to date has been proven. It has structural similarities with phosphatidylcholine in terms of the polar head group, so it is also classified as phospholipid (phosphosphingolipid).
Like the other sphingolipids, sphingomyelin has both structural and cellular signaling functions, and is especially abundant in nerve tissues, specifically in myelin, a sheath that covers and insulates the axons of certain neurons.
Sphingomyelin is an amphipathic molecule composed of a polar head and two apolar tails. The polar head group is a phosphocholine molecule, so it may appear similar to phosphatidylcholine glycerophospholipid (PC). However, there are substantial differences regarding the interfacial and hydrophobic region between these two molecules.
The most common base in a mammalian sphingomyelin molecule is ceramide, composed of sphingosine (1,3-dihydroxy-2-amino-4-octadecene), which has a double trans bond between the carbons of positions 4 and 5 of the hydrocarbon chain. Its saturated derivative, sphinganine, is also common, but is found in a smaller proportion.
The length of hydrophobic tails of sphingomyelin ranges between 16 and 24 carbon atoms and the fatty acid composition varies depending on the tissue.
In the interfacial region of the molecule, sphingomyelin has an amide group and a free hydroxyl in carbon 3, which can serve as donors and acceptors of hydrogen bridges for intra- and intermolecular bonds, important in the definition of lateral domains and interaction With various types of molecules.
