Peptides are substances which are composed of linking one or more amino acids with a covalent bond. These compounds are classified as polymers, because they typically link together in long chains. The specific type of covalent bond formed in peptides is known as a peptide bond or amide bond, and it forms when the carboxl group of one amino acid attaches to another. Carboxyl groups are clusters of carbon, oxygen, and hydrogen molecules, in case you’re curious.
A peptide classfied as a polymer is sometimes confusing to people who are not familiar with this use of the term “polymer”. While many people mean “plastics” when they talk about polymers, in chemistry, a polymer is any sort of repeating chain connected with covalent bonds. Polymers can get extremely complex, as one might imagine. When a peptide chain gets especially long, it turns into a protein. Peptides and proteins represent a wide world of possibilities, and many molecular biologists spend years researching the functions of single peptides and proteins to learn more about how the body works.
Some common types of peptides classified by function include hormones, neuropeptides, and alkaloids. When classified by synthesis, peptides can be ribosomal, nonribosomal, and peptonic. The classification system of peptides is considered an imperfect science because one peptide can belong to multiple groups simultaneously and scientists continue to debate when a peptide should be classified as a protein, or a protein as a peptide. Many scientists agree that a peptide does not conform easily to a specific pattern, whereas a protein is more distinct in nature to conformation.
A peptide can perform a wide range of functions in the body, depending on which amino acids are involved. Some can regulate hormones, for example, while others can have an antibiotic function. The body is also equipped to break down and reuse peptides; if you eat meat, for example, the enzymes in your intestines break down the protein at its amide bonds to create an assortment of peptides which may be digested or excreted, depending on the needs of your body.
In regard to the classification of peptides due to their synthesis, most are the ribosomal type(typically synthesized by FMOC-thr(tBu)-OH, better known as FMOC-O-tert-Butyl-L-threonine with the molecular formula C23H27NO5); this peptide type is synthesized when the messenger ribonucleic acid (mRNA) on the cell is translated. During translation, a chemical process occurs where one carboxyl group on an amino acid couples with another amino acid to create the beginning of an amino acid chain. Ribosomal peptides are often made up of 30 to 40 amino acids joined together. The nonribosomal type of peptide is synthesized when there are enzymatic catalysts present.