Animal fat is used to make soap, and then that soap can be used to remove
animal fat from our hands and clothing. What is soap? Soap can be made
by subjecting lard (pig fat) to saponification, in which heat and a strong
alkali (NaOH or KOH) release fatty acids in the form of sodium or
potassium salts from triacylglycerols. When mixed with water, the fatty
acids in the soap function as amphipathic molecules that form micelles as
a result of the hydrophobic effect. With sufficient agitation, the micelles
trap greasy food particles and are washed away during the rinsing phase.
Unesterified free fatty acids inside cells would also act as soap and disrupt
biological membranes by forming micelles. This is prevented from happening
by maintaining fatty acids inside cells as chemically neutralized
molecules by use of an ester linkage between fatty acids and glycerol to
form triacylglycerols or noncovalent binding of free fatty acids to soluble
carrier proteins.
Everyday BioChem 