Chitin is a polymer of N-acetylglucoseamine, a glucose molecule with an amino and acetic acid group attached to the number 2 carbon. It too has a beta 1-4 linkage. Lipids are molecules that dissolve in non-polar solvents like hexane or ether. Or to put it another way lipids will not dissolve in polar solvents like water. Unlike the other classes of biomolecules which are characterized by their chemical structure, lipids are characterized by the physical characteristic of solubility.
Fatty acids are hydrocarbon chains with a carboxylic acid group at the end.
The higher the number of carbons, the higher the melting point of the fatty acid. Also, the greater the number of unsaturations, the lower the melting point of the fatty acid. Glycerides are lipids in which fatty acids are attached to the glycerol molecule.