Figure 1.

Different roles of lipids. (A) Phosphatidylcholine and cholesterol are major structural lipids. (B) Cholesterol esters and triacylglycerols are used to stored excess fatty acids in cells. They are stored within lipid droplets and endoplasmic reticulum-derived vesicular structures. (C) Diacylglycerol and sphingosine-1-phosphate are signaling lipids. Diacylglycerols affect protein kinase C activity, and sphingosine-1-phosphate promotes proliferation through its interactions with cell surface receptors.