Pepsin: the first enzyme Gastric glands in discovered(18th centur) stomach linin Parietal cells (secrete HCl Chief cells (secrete pepsinogen) Stomach Gastric mucosa Pancreas pepsinogen (secretes gastrin) pepsI Pancreatic duet Exocrine cells of Da互 creas Rough ER pH Zymogen Zymogens granule active proteases Collecting duct Villi of small intestine Small o Villus Intestine. and amin Intestinal mucosa Degradation absorption (absorbs amino acids) of dietary proteins Essential amino acidsProteins (but not pepsin) unfolded Absorbed as tri- & dipeptides, and amino acids Degradation & absorption of dietary proteins Pepsin: the first enzyme discovered (18th century). proteases Essential amino acids