Polymers

Figure 4-13 Two amino acids linked by a dehydrolysis reaction and by a peptide linkage produce a dipeptide.

Amino acids are linked together to produce proteins. Thus, when proteins are digested, they are broken down into amino acids. The link between amino acid units is called a peptide bond. Uniting two amino acids is achieved by removing one molecule of water (known as a dehydrolysis reaction). The coupling takes place between the terminal carbon atom of one amino acid and the nitrogen atom of the other amino acid (figure 4-13). Adding a third amino acid to a union of two amino acids yields a tripeptide. To break such a compound into separate amino acids, one molecule of water must be added to the reaction (a hydrolysis reaction).