AP BIOLOGY

Detailed explanation-1: -Pepsin is a stomach enzyme that serves to digest proteins found in ingested food. Gastric chief cells secrete pepsin as an inactive zymogen called pepsinogen. Parietal cells within the stomach lining secrete hydrochloric acid that lowers the pH of the stomach.

Detailed explanation-2: -An enzyme made in the stomach that breaks down proteins in food during digestion. Stomach acid changes a protein called pepsinogen into pepsin.

Detailed explanation-3: -The hydrochloric acid in the gastric juice breaks down the food and the digestive enzymes split up the proteins. The acidic gastric juice also kills bacteria.

Detailed explanation-4: -Chemical digestion in the small intestine is continued by pancreatic enzymes, including trypsin, chymotrypsin and carboxypeptidase, each of which act on specific bonds in amino acid sequences.

Detailed explanation-5: -Most mechanical and some chemical digestion occur in the stomach. Mechanical digestion occurs as layers of muscle in the stomach lining contract to produce a mixing and churning motion. Chemical digestion is carried out by stomach juices that contain enzymes and hydrochloric acid.