Polar Nature and Emulsifying Properties

Unlike fatty acids, most phospholipids are water-soluble as well as fat-soluble, because their molecules have hydrophobic as well as hydrophilic regions, and are polar in character. For this reason, they are sometimes called amphipathic lipids. 

In general, membrane lipids are amphipathic phosphoesters whereas storage lipids are not. The water solubility tends to decrease rapidly with increasing lengths of the hydrocarbon chains. 

Phospholipids are important for their emulsifying properties. In an oil-water system, the molecules concentrate at the interfaces and lower the sm face tension, thus enabling droplets to be formed. They act as a barrier at the interfaces and stabilise the emulsion. When heated with acids or bases. 

FIGURE 10.31 Surface layers and micelles formed by phospholipids. 

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