At what pH values will lipase likely be denatured? Justify your answer. At what pH values will pepsin likely be denatured? Justify your answer. 9. In addition to being produced in the pancreas, lipase is also produced in the stomach. Is the structure of pancreatic lipase the same as gastric (produced in the stomach) lipase? Justify your reasoning.
The Correct Answer and Explanation is:
Lipase is an enzyme responsible for breaking down lipids (fats) into fatty acids and glycerol. Enzymes function optimally within specific pH ranges, and outside these ranges, they can become denatured—losing their three-dimensional structure and, consequently, their function. Pancreatic lipase operates best at a slightly basic pH, typically around pH 7.5 to 8.5, which corresponds to the environment in the small intestine. At highly acidic pH values (such as pH < 4), the structure of pancreatic lipase is likely to be disrupted due to the high concentration of hydrogen ions interfering with ionic bonds and hydrogen bonding in the enzyme’s tertiary structure. Therefore, pancreatic lipase will likely be denatured at low pH values, such as in the stomach (pH 1–3).
In contrast, pepsin is a proteolytic enzyme secreted by the chief cells of the stomach as an inactive precursor, pepsinogen. It becomes activated in the acidic environment of the stomach (optimal at pH 1.5 to 2). This extremely low pH maintains the active conformation of pepsin and facilitates its enzymatic activity. Pepsin is denatured at higher pH values (above pH 6), where the decrease in hydrogen ion concentration causes changes in the enzyme’s shape, disrupting its active site and rendering it nonfunctional.
Although both pancreatic and gastric lipases catalyze the hydrolysis of fats, their structures are not identical. Pancreatic lipase and gastric lipase are encoded by different genes and are adapted to function in very different pH environments—neutral to slightly basic in the small intestine and acidic in the stomach, respectively. To perform optimally in these different conditions, the two types of lipase have different amino acid sequences and tertiary structures. This structural variation allows them to remain stable and functional in their respective environments, confirming that their structures are not the same.
