Properties of Polymers
Types of Biological Macromolecules
Biological macromolecules, the large molecules necessary for life, include carbohydrates, lipids, nucleic acids, and proteins.Learning Objectives
Identify the four major classes of biological macromoleculesKey Takeaways
Key Points
- Biological macromolecules are important cellular components and perform a wide array of functions necessary for the survival and growth of living organisms.
- The four major classes of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids.
Key Terms
- polymer: A relatively large molecule consisting of a chain or network of many identical or similar monomers chemically bonded to each other.
- monomer: A relatively small molecule that can form covalent bonds with other molecules of this type to form a polymer.

Sources of biological macromolecules: Foods such as bread, fruit, and cheese are rich sources of biological macromolecules.

Living organisms are made up of chemical building blocks: All organisms are composed of a variety of these biological macromolecules.
Monomers and Polymers
Biological macromolecules play a critical role in cell structure and function. Most (but not all) biological macromolecules are polymers, which are any molecules constructed by linking together many smaller molecules, called monomers. Typically all the monomers in a polymer tend to be the same, or at least very similar to each other, linked over and over again to build up the larger macromolecule. These simple monomers can be linked in many different combinations to produce complex biological polymers, just as a few types of Lego blocks can build anything from a house to a car.Monomers and polymers: Many small monomer subunits combine to form this carbohydrate polymer.

The molecule sucrose (common table sugar): The carbohydrate monosaccharides (fructose and glucose) are joined to make the disaccharide sucrose.
Four Classes of Biological Macromolecules
There are four major classes of biological macromolecules:- carbohydrates
- lipids
- proteins
- nucleic acids
Each of these types of macromolecules performs a wide array of important functions within the cell; a cell cannot perform its role within the body without many different types of these crucial molecules. In combination, these biological macromolecules make up the majority of a cell's dry mass. (Water molecules make up the majority of a cell's total mass.) All the molecules both inside and outside of cells are situated in a water-based (i.e., aqueous) environment, and all the reactions of biological systems are occurring in that same environment.