The correct answer is "Chief cells; hydrochloric acid secreted by parietal cells".
Explanation:
Pepsinogen is produced by chief cells in the gastric system. Pepsinogen is a precursor of pepsin, a powerful digestive enzyme that is activated when pepsinogen is exposed to gastric acid in the gastric lumen. This gastric acid is actually hydrochloric acid that is secreted by parietal cells, which are epithelial cells located in the gastric glands.
Pepsinogen is produced by chief cells and is activated by hydrochloric acid secreted by parietal cells.
Explanation:
Pepsinogen is a proenzyme produced in the chief cells (that are located in the stomach lining) that, when gets activated, is transformed into pepsin - a peptidase with the function to degrade proteins into amino acids.
The reason why pepsinogen is released inactive is that it would break down all of the cell's proteins because of its proteolytic nature. For this reason, it is released as a proenzyme and gets activated when reaches the acidic environment provided by the hydrochloric acid secreted by the parietal cells, also in the stomach lining.
