MCQ Detailed View

Digestion is the process of breaking down complex food molecules into simpler forms that can be absorbed and utilized by the human body. This process begins in the mouth, where the teeth physically break food into smaller pieces while saliva provides the first step of chemical digestion.

Saliva is secreted by the salivary glands and contains salivary amylase (also called ptyalin), an enzyme that specifically targets starch, a complex carbohydrate. Starch molecules are long chains of glucose units. When saliva mixes with food, salivary amylase breaks starch into smaller sugar units, mainly maltose (a disaccharide). This makes starch easier to digest later in the small intestine, where other enzymes complete the process to release glucose for energy.

Other nutrients such as proteins, lipids, and fats are not digested in the mouth. Protein digestion begins in the stomach with the action of the enzyme pepsin. Fats and lipids are mainly digested in the small intestine with the help of bile salts (from the liver) and the enzyme lipase (from the pancreas). Therefore, saliva’s role is specific to the early digestion of carbohydrates, not other macronutrients.

This initial breakdown in the mouth is important because it reduces the digestive workload for later stages and ensures efficient absorption of glucose in the intestine. In addition, saliva helps moisten food, making swallowing easier, and has protective functions like maintaining oral hygiene by washing away food particles and preventing infections.

In summary, the nutrient that saliva helps digest is starch (carbohydrates), making the mouth the very first site of chemical digestion in the human digestive system.