Lipids are water insoluble organic compounds.
They dissolve well in organic solvents such as ether and alcohol. The molecular chemical structure of lipids is very variable. We'll give you a sense of the chemical composition of oils and fats and some of the key components of this group.
Oil and fat - belong to the category of esters and are formed by the reaction of a alcohol, called glycerol, with long chain organic acids known as fatty acids. As with carbohydrates, the reaction of glycerol with fatty acids is condensation, with release of water molecules.
Since glycerol is a tri-alcohol (has three OH termini in the molecule), three fatty acids attach to it, forming the so-called triglycerides. In living beings, there are several types of triglycerides, since there are many types of fatty acids in them.
With respect to fatty acids participating in a triglycerides, remember that they are long chain substances. At one end of each fatty acid is an acidic portion (the “head”), followed by a long “tail” formed by a sequence of carbon atoms attached to hydrogen atoms.
In so-called saturated fatty acids, all available bonds of carbon atoms are occupied by hydrogen atoms. In unsaturated fatty acids, however, not all carbon bonds are occupied by hydrogen; consequently, what in chemistry is known as double bonding between one carbon atom and the next (which is why the fatty acid is called unsaturated) is formed. In polyunsaturated fatty acids there is more than one double bond.