How does the stomach contribute to chemical digestion?

The stomach contributes to chemical digestion by secreting gastric juice, which contains hydrochloric acid and digestive enzymes.

The stomach plays a crucial role in the process of chemical digestion. This organ is responsible for breaking down food into a semi-liquid substance called chyme, which is then passed on to the small intestine for further digestion and absorption. The stomach achieves this through the secretion of gastric juice, a potent cocktail of hydrochloric acid, digestive enzymes, and mucus.

Hydrochloric acid, produced by the parietal cells in the stomach lining, creates an acidic environment with a pH of around 1.5 to 3.5. This acidity serves two main purposes. Firstly, it denatures proteins in the food, unravelling their complex structures and making them more accessible to enzymatic action. Secondly, it provides the optimal pH for the function of the enzyme pepsin.

Pepsin, secreted by the chief cells in the stomach lining, is the main digestive enzyme at work in the stomach. It is initially produced as the inactive precursor pepsinogen, which is activated by the acidic environment to become pepsin. Pepsin then begins the process of protein digestion, breaking down proteins into smaller peptides.

The mucus produced by the stomach lining serves to protect the stomach itself from the corrosive effects of the hydrochloric acid and pepsin. It forms a barrier that prevents the stomach tissue from being digested along with the food.

In summary, the stomach contributes to chemical digestion by creating an acidic environment that denatures proteins and activates pepsin, and by secreting the enzyme pepsin that begins the process of protein digestion. The mucus it produces protects the stomach lining from these potent substances.