MCAT Question A Day - 7/14/14 - Answer!
As chyme is passed from the stomach. to the small intestine, the catalytic activity of pepsin:
A. increases because pepsin works synergistically with trypsin.
B. increases because pepsin is activated from its zymogen form.
C. decreases in response to the change in pH.
D. decreases because pepsin is digested by pancreatic amylase in the small intestine.
C is correct. Pepsin, whose optimum pH is around 2.0, denatures in the environment of the small intestine, whose pH is between 6 and 7. A is wrong because pepsin isn't working at all in the small intestine; it won't be working synergistically with trypsin. B is wrong because pepsinogen is activated in the stomach by low pH. D is wrong because pepsin is a catalyst, which makes it a protein; amylase digests starch.
Want more questions? - Click here to check out our MCAT Question A Day archive
C is correct. Pepsin, whose optimum pH is around 2.0, denatures in the environment of the small intestine, whose pH is between 6 and 7. A is wrong because pepsin isn't working at all in the small intestine; it won't be working synergistically with trypsin. B is wrong because pepsinogen is activated in the stomach by low pH. D is wrong because pepsin is a catalyst, which makes it a protein; amylase digests starch.
Want more questions? - Click here to check out our MCAT Question A Day archive
