 Monomers are the simple subunits that are used to make polymers. Carbohydrates, proteins, and nucleic acids in biological systems are polymers. One way to think about the process of making and breaking down polymers is to use beads like this to visualize the process. Single monomers, represented by the single beads, are linked together to form a chain. A polymer, then, is a long chain, like this one, of linked monomers. They can all be the same monomer as in this chain. For example, starch is a long chain of glucose monomers, or the monomers can all be different, like in proteins and nucleic acids. Nucleic acids are made up of four different nucleotide monomers, whereas proteins are made up of up to 20 different amino acid monomers. Polymers are broken down via a hydrolysis reaction. The polymers can first be broken into smaller polymers, and then those smaller polymers can be broken down, or monomers can be broken off the end one by one until you're left with just single monomers again.