Question

Gastric digestion takes place efficiently in
A. Acidic medium
B. Alkaline medium
C. Neutral medium
D. Highly alkaline medium

Answer 1

Hint: Gastric digestion requires activation of certain enzymes present within the stomach itself. The stomach environments and gastric secretions help with their activation. Protein digestion primarily occurs within the stomach due to presence of the protein digesting enzymes.

Complete answer:
Stomach is an important part of the human digestive system. This muscular organ secretes enzymes and hydrochloric acid that help in digestion of various food components. As the food enters the stomach, the proteins present in food are mainly hydrolyzed first and broken down with action of proteolytic enzymes. Protein hydrolysis is influenced due to the acidic medium (pH of about 1.5-3.5) of stomach, which is maintained with secretion of hydrochloric acid. In addition to this, the acid is also responsible for activation of the inactivated protein-digesting enzymes or pepsinogen.
The pepsinogen (inactivated form of enzyme) is converted to its active form called pepsin in presence of hydrochloric acid. This pepsin enzyme acts on proteins for their hydrolysis. The enzymes require certain optimum conditions of pH, temperature, and others for their efficient activity. Therefore, in case of gastric digestion, enzymes function optimally in acidic medium instead of alkaline, highly alkaline or neutral medium. In an alkaline or neutral medium, activation of enzymes would be affected. As a result, protein hydrolysis (which is the main process occurring in the stomach) might not be taking place efficiently in the stomach.

The correct answer is option A, stating “acidic medium”.

Note:
Enzymes are the proteins that have catalytic activity. These are generally substrate-specific, and require suitable conditions for catalysing a reaction, for example – conversion of inactivated pepsinogen into active pepsin in the stomach. The enzyme activity subsequently decreases at conditions other than optimum.