Macromolecules are long polymeric molecules formed by the combination (via covalent bonds) of many individual units known as monomers. Organic macromolecules important in the body are polypeptides (composed of amino acids), carbohydrates (composed of mono/disaccharides), lipids (composed of a combination of glycerol, fatty acids and phosphates) and nucleic acids (composed of nucleotides). Lipids are somewhat different from the others in that they do not possess the ability to form long chains of repeating units, but are limited to forming smaller molecules such as triglycerides.
The joining of the individual monomers to form macromolecules is achieved through condensation reactions, which are catalysed by enzymes. The process of macromolecule formation is vital to living organisms, as it allows the creation of the higher structures that are required for life to continue.