The structure of lipids and their biological functionsFats and oils are substances composed 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. They both contain carbon, hydrogen and oxygen atoms, but less oxygen than in a carbohydrate. The formula for glycerol is C3H8 O3 and the arrangement of the atoms is shown in the following diagram: The formula for a fatty acid is much more complex because they vary in size depending on which lipid it is to be a part of. A generalized formula for a fatty acid is The n is determined by the number of carbons attached to two hydrogens, but n is normally around about 16. So the fatty acid molecule above has the formula because it has 6 carbons with hydrogen atoms attached. The carboxyl group highlighted in pink terminates 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 eliminated and an oxygen bond (Ester bond in this case) is established. As I mentioned earlier, some fatty acids can have around 16 CH2 bonds. In some cases, not all carbon atoms have a hydrogen atom attached to them and this type of fatty acid is therefore called "unsaturated." " whereas as if all the bonds were full we say "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..