In biology, a polymer is a large molecule composed of many similar smaller molecules linked together in a chain-like fashion. These smaller molecules are called monomers, and when they are linked together, they form a long chain called a polymer. Polymers make up many of the materials in living organisms, including proteins, cellulose, and nucleic acids. Organic polymers play a crucial role in living things, providing basic structural materials and participating in vital life processes. There are three major classes of biopolymers: polysaccharides, polypeptides, and polynucleotides. Examples of natural polymers include cellulose, shellac, and amber. Biopolymers such as proteins and nucleic acids play crucial roles in biological processes.