triglyceride, any one of an important group of naturally occurring lipids (fat-soluble components of living cells). Triglycerides are esters in which three molecules of one or more different fatty acids are linked to thealcohol glycerol; they are named according to thefatty acid components;e.g., tristearin contains three molecules ofstearic acid, and oleodistearin, one ofoleic acid and two of stearic acid. The types of triglycerides in animals vary with the species and thecomposition of fats in the food.

Triglycerides in animals and probably in plant seeds function as depots of energy. In mammals they are stored inadipose tissue until needed, at which time they are broken down to amolecule ofglycerol and three molecules of fatty acid. The latter combine with albumin, a protein inblood plasma, and are carried in the bloodstream to sites of utilization. Triglycerides also serve as insulation and padding for organs in animals.

Many vegetable triglycerides (oils) areliquid at room temperature, unlike those of animals; in addition, they contain a greater variety of fatty acids. Vegetable oils can be hardened bytreatment with hydrogen under pressure.

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lipid: Digestion of dietary fatty acids

In alkali, triglycerides are broken down (saponified) to form glycerol and three molecules of soap (salts of the fatty acids).