The absorption of proteins, or more precisely amino acids, occurs in the small intestine. Proteins are often huge molecules which must be broken down into amino acids and peptides that are small enough for the small intestine to absorb. After this, the amino acids are sent into the bloodstream.
The digestion of proteins begins in the stomach, where powerful hydrochloric acid begins the breakdown of the protein molecules. Along with stomach acid, the protein is partially broken down by an enzyme called pepsin. Pepsin is noteworthy because the acid in the stomach does not damage it. It works best in a highly acidic environment.
After the protein is partially degraded in the stomach, it continues to the small intestine, where it is further broken down by enzymes and juices secreted by the pancreas. These enzymes break the proteins down into amino acids and peptides that contain two or three amino acids. It is important that the body be able to absorb amino acids, for there are nine that the body needs but does not synthesize.
Proteases that are secreted by the cells that line the intestine further contribute to the breakdown of protein. These amino acids and peptides are then sent by the intestine into the bloodstream.