Final answer:
Amylase starts the digestion of carbohydrates in the mouth by breaking down starch into simpler sugars; the process stops once the food reaches the stomach.
Step-by-step explanation:
The student has a question about the role of amylase in the digestive system. Amylase is an enzyme that begins the digestion of carbohydrates in the mouth. As food enters the mouth, amylase in the saliva starts breaking down starch, which is a type of carbohydrate, into simpler sugars like maltose. This process halts when the food reaches the acidic environment of the stomach, where amylase is inactivated, allowing other digestive processes to take over for different macronutrients.
Meanwhile, the digestion of proteins begins in the stomach with enzymes like pepsin, and fats are predominantly digested in the small intestine with the help of bile and pancreatic lipase. Iron is absorbed in the small intestine and does not undergo a digestion process like macronutrients do. Therefore, the correct answer to the student's question is: Amylase begins the digestion of carbohydrate in the mouth.