Where is pancreatic lipase most active, and why is it active there?

• A. It is most active only in the mouth.
• B. It is most active only in the pancreas.
• C. It is most active in environments with pH around 7.0, such as the mouth and pancreas.
• D. It is most active in acidic environments around pH 2.0.

Answer: (C)

Pancreatic lipase works best when the environment is near neutral pH. Around pH 7, the enzyme’s catalytic site residues are properly ionized to drive the hydrolysis of triglycerides efficiently. In the stomach, the acidic conditions would disrupt this, while in the small intestine, bicarbonate released from the pancreas neutralizes the chyme to about pH 7, creating optimal conditions for the enzyme to function. Bile salts also help by emulsifying fats, increasing surface area for the lipase to act. So, the neutral pH around 7—found in the intestinal lumen (and closely approximated in the mouth)—is where pancreatic lipase is most active.