What is the optimal pH range for the activity of pepsin?

• A. Between 6.5 and 7.5
• B. Around 4.0 to 5.0
• C. Around 1.5 to 2.0
• D. Between 8.0 and 9.0

Answer: (C)

Pepsin is a digestive enzyme that is primarily active in the stomach, where it plays a crucial role in breaking down proteins into smaller peptides. The optimal pH range for pepsin activity is around 1.5 to 2.0, which is highly acidic. This acidic environment is provided by the gastric juices in the stomach, which contain hydrochloric acid.

The reason for this optimal acidic pH is that pepsinogen, the inactive precursor of pepsin, is activated to pepsin in acidic conditions. Once activated, pepsin functions best under these conditions by facilitating the hydrolysis of peptide bonds in proteins.

When pepsin is exposed to a pH outside of its optimal range, particularly in more neutral or basic conditions, its activity decreases significantly, leading to reduced protein digestion. Thus, the correct answer highlights the specific environment in which pepsin operates most effectively, aligned with its biological role in the digestive system.