Final answer:
The three most common phospholipids are phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. Sphingomyelin, a type of sphingophospholipid, has a choline group attached to the phosphate group at its end and is vital for the structure of myelin sheaths in nerve cells.
Step-by-step explanation:
The three most common phospholipids found in biological membranes are phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine. Each of these phospholipids consists of a glycerol backbone with two fatty acid chains (hydrophobic tails) and a phosphate group (hydrophilic head) modified by an alcohol such as choline, ethanolamine, or serine, respectively.
As for sphingomyelin (SM), it is a type of sphingophospholipid which is built upon a sphingosine backbone rather than glycerol. Sphingomyelin is unique as it contains a fatty acid attached to the amino group of sphingosine, forming ceramide, and a phosphoric acid attached to the primary alcohol group. Finally, the base choline is attached to this phosphate group, which is the group on the end of sphingomyelin.
Sphingomyelins are crucial components of cell membranes, especially in the myelin sheath of nerve cells. Damage to sphingomyelin-containing myelin sheaths can result in diseases such as multiple sclerosis.