Sphingolipids are distinguished from glycerolipids by having which backbone?

• A. A glycerol backbone
• B. A cholesterol backbone
• C. A glucose backbone
• D. A sphingosine backbone

Answer: (D)

The main distinction here is the backbone the lipid is built on. Sphingolipids use a sphingosine backbone, an 18-carbon amino alcohol, as the core structure. A fatty acid attaches to sphingosine by an amide bond to form ceramide, and different head groups give the various sphingolipids. Glycerolipids, in contrast, have glycerol as their backbone with two fatty acids attached and a phosphate or other head group at the third carbon. So the correct backbone that sets sphingolipids apart is the sphingosine backbone. The other options don’t define sphingolipids: glycerol is the backbone of glycerolipids, cholesterol is a sterol not the backbone of these lipids, and glucose isn’t used as a lipid backbone.