What is the Difference Between Protein Digestion in Stomach and Small Intestine?

Protein digestion occurs in the stomach and small intestine, with the majority of digestion taking place in the small intestine. The main differences between protein digestion in the stomach and small intestine are as follows:

Stomach:

• The stomach releases gastric juices containing hydrochloric acid and the enzyme pepsin, which initiate the breakdown of the protein.
• Pepsin breaks down proteins into smaller polypeptides.
• Protein digestion in the stomach takes longer than carbohydrate digestion but shorter than fat digestion.
• The stomach's powerful mechanical contractions churn the partially digested protein into a more liquid state, known as chyme.

Small Intestine:

• The pancreas secretes digestive juices into the small intestine, containing more enzymes to further break down polypeptides.
• The two major pancreatic enzymes that digest proteins are chymotrypsin and trypsin.
• The cells lining the small intestine release additional enzymes that finally break apart the polypeptides into tripeptides, dipeptides, and individual amino acids.
• The muscle contractions of the small intestine mix and propel the digested proteins to the lower parts of the small intestine, where amino acids are transported from the intestinal lumen through the intestinal cells to the blood.

In summary, the stomach initiates protein digestion by breaking down proteins into smaller polypeptides, while the small intestine completes the process by further breaking down polypeptides into individual amino acids, which can then be absorbed into the bloodstream.

Comparative Table: Protein Digestion in Stomach vs Small Intestine

The table below highlights the differences between protein digestion in the stomach and small intestine:

In the stomach, protein digestion is catalyzed by hydrochloric acid (HCl) and pepsin, which break down proteins into amino acids and oligopeptides. The digestion process then moves to the small intestine, where the majority of protein digestion occurs. The pancreas secretes digestive juices containing enzymes such as trypsin, chymotrypsin, aminopeptidase, and dipeptidase, which further break down the polypeptides into dipeptides and amino acids. Once in the lower parts of the small intestine, the amino acids are transported from the intestinal lumen through the intestinal cells to the blood.