Answer:
The image shows a graph depicting the optimal pH ranges for three enzymes involved in digestion: pepsin, amylase, and trypsin. The optimal pH range for pepsin is between 2 and 4, for amylase it is between 6 and 8, and for trypsin, it is between 7 and 9.
Question: Given what you know about enzymes, why does amylase work best in the mouth and not in the stomach?
Answer:
Amylase works best in the mouth because the pH in the mouth is typically around 6 to 7, which falls within the optimal pH range for amylase activity (6 to 8). The stomach, however, has a highly acidic environment with a pH between 2 and 4 due to gastric acid. This acidic environment is optimal for pepsin activity but not for amylase. Therefore, amylase, which begins carbohydrate digestion in the mouth, becomes inactive in the acidic conditions of the stomach.
When food moves from the mouth to the stomach, the enzymes from the mouth move with it. However, once in the stomach, the acidic environment denatures (inactivates) amylase. Consequently, amylase cannot function effectively in the stomach, halting the digestion of carbohydrates until the food reaches the small intestine, where the pH is more neutral to slightly alkaline, and pancreatic amylase can resume carbohydrate digestion.