Was your prediction correct about the optimal pH for pepsin activity? Best description

Was your prediction correct about the optimal pH for pepsin activity? Best description

• A. Highest at pH 2.0, lower at pH 7.0 and 9.0
• B. Highest at pH 7.0
• C. Highest at pH 9.0
• D. Activity is the same at all pH

Answer: (A)

Pepsin works best in acidic conditions; its active site is optimally protonated in the highly acidic environment of the stomach, around pH 2.0, which enables efficient peptide bond cleavage. When the pH moves toward neutral or basic values, pepsin’s structure and charge state shift in ways that reduce or disable its catalytic activity, so it shows much lower activity at pH 7.0 or 9.0. This is why the description stating that pepsin activity is highest at pH 2.0 and lower at pH 7.0 and 9.0 matches what we know about the enzyme. The idea that activity would be the same across pH or that the optimum would be at neutral or basic pH does not fit pepsin’s stomach-based, acid-dependent function.

Pepsin works best in acidic conditions; its active site is optimally protonated in the highly acidic environment of the stomach, around pH 2.0, which enables efficient peptide bond cleavage. When the pH moves toward neutral or basic values, pepsin’s structure and charge state shift in ways that reduce or disable its catalytic activity, so it shows much lower activity at pH 7.0 or 9.0. This is why the description stating that pepsin activity is highest at pH 2.0 and lower at pH 7.0 and 9.0 matches what we know about the enzyme. The idea that activity would be the same across pH or that the optimum would be at neutral or basic pH does not fit pepsin’s stomach-based, acid-dependent function.