Question

Enzyme functional at pH 2 is
(a)Trypsin
(b)Pepsin
(c)Lipase
(d)Ptyalin

Answer 1

pH 2 indicates that the environment is acidic. So enzymes that require an acidic environment will function at that pH. An enzyme that is used for the digestion of proteins in the stomach functions in an acidic environment.

Complete answer:
The stomach is a bag-like organ that has an acidic environment. The enzyme pepsin present in the stomach helps in the digestion of proteins and requires an acidic pH for functioning. It is secreted in the stomach as inactive zymogen called pepsinogen which is converted to pepsin by the acidic pH of the stomach which is the active form.
Pepsin is an endopeptidase hormone that breaks down the proteins into smaller peptides. They are produced in the chief cells of the stomach lining. Pepsin is most active with an optimum pH of 1.2 to 2.5 and its primary site of synthesis and activity is in the stomach.

Additional Information:
-Pepsin is inactivated if the pH is 6.5 or above. It gets permanently inactivated and denatured at a pH of 8.
-The optimum pH for the activity of Trypsin is 7.8-8.7.
-The optimum pH for the activity of enzyme lipase ranges from neutral to slightly basic.
-The enzyme ptyalin or salivary amylase which breaks down the sugars in the mouth and begins the digestion of carbohydrates functions in a slightly acidic pH ranging from 5.6-6.9.
So, the correct answer is, “Pepsin.”

Note: -The enzyme ptyalin which starts the digestion of carbohydrates becomes inactive as it enters the acidic pH of the stomach. So, the acidic pH of the stomach facilitates the functioning of Pepsin and thus helps in the digestion of proteins, but it stops the digestion of carbohydrates.
-The acidic pH of the stomach is mainly due to the hydrochloric acid present in the stomach which provides the optimum pH. However, the hypersecretion of this acid may lead to ulcers and acid reflux.