These molecular diagrams illustrate the structural differences between saturated fats and the essential dietary oils. The bent shape of the essential fatty acids keeps them from dissolving into each other. LA and LNA possess a slightly negative charge and have a tendency to form very thin surface layers. This property is called surface activity, and it provides the power to carry substances like toxins to the surface of the skin, intestinal tract, kidneys and lungs where they can be removed. Plants have enzymes capable of inserting these double bonds starting at the third carbon atom.
Human enzymes can make double bonds starting at the ninth carbon atom only.
If the fatty acid has just one double bond it is called a monounsaturated fatty acid. If the fatty acid has more than one double bonded carbon pair it is polyunsaturated. Linoleic acid has two unsaturated pairs in its 18-carbon chain. Linolenic acid has three pairs in its 18-carbon chain. These unsaturated bonds cause the normally straight line shape of the carbon chain to bend at the double bonded pair because nature always removes the hydrogen atoms from the same side of the fatty acid molecule.