Pepsin, classified as an enzyme, performs important digestive functions. Digestion describes the process by which the digestive tract breaks down food particles into smaller molecules the body can absorb. Digestion occurs through mechanical processes, such as chewing, and chemical processes, performed by a variety of hormones and enzymes.
Pepsin Production
The process of chemical digestion begins when food reaches the stomach, which stimulates the stretch receptors. These receptors send signals to the portion of the brain known as the medulla oblongata. The medulla oblongata stimulates the endocrine cells within the lining of the stomach to produce and release gastrin, a hormone, into the bloodstream. The circulation of gastrin stimulates the stomach to release gastric, or digestive, juices.
The presence of gastrin in the blood also stimulates specific cells in the lining of the stomach to produce an inactive form of pepsin known as pepsinogen. Once pepsinogen enters the stomach cavity and mixes with the acidic gastric juices, it converts to pepsin. The presence of pepsin triggers the production of more pepsin, known as a positive feedback loop as described by The University of Cincinnati.
Break Down Proteins
The stomach must break down all food products entering the stomach into small particles in order to be absorbed into the bloodstream and used by the body. Proteins, found in meats, eggs or dairy products, are more difficult to digest than other types of foods. Once the proteins enter the stomach, the hydrochloric acid found in gastric juices changes the shapes of proteins, thereby exposing the bonds, a process known as denaturing. This makes the proteins more vulnerable to the effects of pepsin.
When pepsin comes into contact with denatured proteins, it breaks the bonds holding together the amino acids--the building blocks of proteins. Pepsin cannot break all protein bonds, but the resulting small peptides can be transported into the small intestine for further digestion.
Further Digestion
The small peptides formed by pepsin enter the small intestines, an organ within the digestive tract about three meters long, according to Clinton Community College. The majority of the digestive process takes place within the small intestine. The pancreas, a gland located in the abdomen between the stomach and the spine, produces many important digestive enzymes, including trypsin--another enzyme that breaks down proteins. Like pepsin, trypsin cannot break all bonds, therefore producing smaller peptide chains.
The mucus membrane of the small intestines secretes another digestive enzyme known as peptidase. Peptidase can break down proteins into the amino acids, which can then be absorbed by the small intestine. Without the pepsin in the stomach, however, these other enzymes would not be able to break down the proteins. Successful digestion of proteins depends upon the combined efforts of pepsin, trypsin and peptidases.
