HTHSCI 1LL3 Lecture Notes - Lecture 16: Chyme, Enzyme, Zymogen
9 Apr 2018
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Document Summary
Begins in the stomach (other than mechanical breakdown in the mouth) Hydrochloric acid (released by the gastric parietal cells) first denatures the proteins- this makes it easier for pepsin to cleave. Pepsinogen (secreted by the gastric chief cells) is the zymogen (enzyme in an inactive form- needs cleavage to convert to active form) form of pepsin. Hcl in the stomach allows for the autocatalytic conversion to pepsin. Pepsinogen needs to be activated to pepsin ph for enzyme function. This allows for denaturing of proteins (and then cleavage) Intestines need a ph of 6 for digestive enzymes. This quick change in ph is achieved through bicarb ions from the pancreas. Once the food enters the duodenum the pancreas releases enzymes & bicarbonate ions. Keep the enzyme inactivated, until it leaves the pancreas so that it won"t break itself down. This neutralizes the acidic chyme so the intestinal enzymes can function. The pancreatic proteases are all released as zymogens.
