Final answer:
The digestion of macronutrients begins in the mouth with the enzyme action on carbohydrates, where amylase starts breaking down starch. Significant digestion of fats and proteins primarily takes place later, in the stomach (proteins) and small intestine (fats).
Step-by-step explanation:
Digestion of Macronutrients
The digestion of macronutrients begins in the mouth, where the breakdown of carbohydrates starts. Salivary amylase is the enzyme that initiates the process by converting starches into maltose, a disaccharide. This action takes place in the oral cavity, as food is mixed with saliva. While it is true that enzymes in saliva also begin to digest starches and fats, the digestion of fats does not significantly occur in the mouth. Protein digestion, on the other hand, predominantly occurs in the stomach aided by the enzyme pepsin and the acidic environment provided by hydrochloric acid (HCl).
Therefore, referring to the question about the digestion of macronutrients in the mouth with enzyme action, the correct answer is a. carbohydrates, fats, and proteins. However, it should be noted that while enzymes for all these macronutrients are present in the saliva, the actual significant digestion of fats and proteins does not begin in the mouth.
Additionally, option c from the reference question states that bile emulsifies lipids in the small intestine, not the large intestine, making option f from the reference question incorrect.