The structure of lipids and their biological functionsFats and oils are substances made up of glycerol and fatty acids and the only difference between fats and oils is that fats are solid at room temperature while oils are not. Both contain carbon, hydrogen and oxygen atoms but less oxygen than a carbohydrate. The formula of glycerol is C3H8 O3 and the arrangement of the atoms is shown in the following diagram: The formula of a fatty acid is much more complex as they vary in size depending on the lipid of which it is to be part. A generalized formula for a fatty acid is n is decided by the number of carbon atoms attached to two hydrogens, but n is normally around about 16. So the above fatty acid molecule has the formula because it has 6 carbon atoms at to which hydrogen atoms are attached. The carboxyl group highlighted in pink ends the molecule and gives it an acidic nature and it is at this terminal group that the bond between glycerol and fatty acids occurs. Fatty acids and glycerol are the subunits of a lipid and in the synthesis of a fat or oil a triglyceride is formed by the combination of three fatty acids with a glycerol. (Monoglyceride - glycerol and 1 fatty acid, diglyceride - glycerol and 2 fatty acids) The way they bond is again a condensation reaction which simply means that water (H20) (in this case three water molecules) is removed and an oxygen bond (Ester Bond in this case). As I said before, some fatty acids can have around 16 CH2 bonds. In some cases not all carbon atoms have a hydrogen atom attached to them and therefore this type of fatty acid is called "unsaturated" "where as if all the bonds were full it is called "saturated". Since the carbon atoms must always have four bonds leading from them, a double bond is created between two carbon atoms in the chain.