Final answer:
The esophagus transports food from the mouth to the stomach without using digestion enzymes. Salivary amylase in the mouth begins carbohydrate digestion, while pepsin in the stomach starts the protein digestion. Further digestion occurs in the small intestine with several enzymes like pancreatic amylase, lipases, and proteases.
Step-by-step explanation:
The esophagus is primarily responsible for transporting food from the mouth to the stomach and does not play a significant role in the chemical digestion of food. Thus, the esophagus does not use enzymes for digestion. However, enzymes are active in other parts of the upper gastrointestinal tract. For example, salivary amylase produced in the mouth helps break down carbohydrates into simpler sugars like maltose. The acidic environment in the stomach halts the activity of amylase.
Once food reaches the stomach, pepsin is the main enzyme at work. It begins the digestion of proteins, breaking them down into smaller peptides. This acidic environment of the stomach, with a pH between 1.5 and 2.5, is ideal for the functioning of pepsin.
The process of digestion continues in the small intestine with a host of other enzymes. Here, enzymes like pancreatic amylase, lipases, and proteases further breakdown carbohydrates, fats, and proteins respectively. The nutrients then get absorbed through the walls of the small intestine into the bloodstream.