Triacylglycerol, a lipid biological macromolecule, is important for long-term energy storage in animals. Triacylglycerols are a family of molecules: glycerol is the parent compound, and structural diversity is achieved by the composition of the three fatty acid components, which are attached via an ester linkage. The fatty acids are hydrocarbon chains (from 12 to 18 carbons in length), and thus hydrophobic. Being hydrophobic, triacyglycerols are stored as insoluble aggregates in adipose tissue, more commonly called fat. Energy is retrieved upon breakage of the C-C bonds, which are reduced (as opposed to oxidized) and thus produce more energy upon oxidation.
The function of triacylglycerol compares with another mammalian storage molecule, the polysaccharide glycogen, which is used for short-term energy storage. The monosaccharide component, glucose, is oxidized (C-O bonds) compared to reduced fatty acids (CH2 bonds), and thus releases less bond energy upon breakage.
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