Pepsin converts proteins into proteoses and peptones present in the stomach. Pepsin is a component of the gastric juice secreted by stomach cells.

Pepsin:
Pepsin is an enzyme that is secreted by the chief cells in the stomach lining. It is an active form of the precursor protein pepsinogen. Pepsinogen is activated by the acidic environment of the stomach and converted into pepsin. Pepsin plays a crucial role in the digestion of proteins.

Function of Pepsin:
Pepsin breaks down proteins into smaller fragments known as proteoses and peptones. Proteins are long chains of amino acids, and the action of pepsin helps to break these chains into smaller peptides. This process is essential for the absorption and utilization of amino acids by the body.

Mechanism of Action:
Pepsin works by cleaving peptide bonds between specific amino acid residues. It primarily targets peptide bonds adjacent to the amino acids phenylalanine and leucine. These bonds are relatively weak and susceptible to hydrolysis by pepsin.

Optimal Conditions for Pepsin Activity:
Pepsin functions optimally in an acidic environment with a pH range between 1.5 and 3.5. The highly acidic conditions in the stomach provide an ideal environment for pepsin activity. However, pepsin activity is inhibited in more alkaline conditions, such as those found in the small intestine. Therefore, its action is limited to the stomach.

Role in Protein Digestion:
Pepsin is one of the key enzymes involved in protein digestion. It acts on dietary proteins, such as those derived from meat, fish, and dairy products. The action of pepsin breaks down these proteins into smaller peptide fragments, which can then be further digested by other enzymes in the small intestine.

Summary:
Pepsin is an enzyme secreted by the stomach lining. It converts the inactive precursor pepsinogen into its active form. Pepsin functions optimally in the acidic environment of the stomach and breaks down proteins into proteoses and peptones. This action is crucial for the digestion and absorption of dietary proteins.