Question

The chemical digestion of food starts in the
A) Mouth
B) Stomach
C) Esophagus
D) Small intestine
E) Large intestine

Answer 1

Hint: Digestion is the process by which complex molecules present in food are broken down into simple molecules so that it can readily be absorbed by the body.

Complete answer:
Before we find the correct option, let us understand the term chemical digestion. The process by which the chemical bonds present in the food are broken down when the enzymes present in the digestive tract act on it is known as chemical digestion.

> Option A: The process of chemical digestion begins in the mouth itself. In the mouth, salivary glands are present which secrete saliva. The saliva contains salivary amylase which acts on the starch present into simpler form.
In the mouth, because of the process of chewing or mastication the food is churned with saliva and this is known as bolus. The bolus is then transferred to the esophagus and then to the stomach. Therefore, this is the correct option.
> Option B: In the stomach, carbohydrates and proteins are digested by the enzymes. It also produces enzymes and hydrochloric acid which helps in maintenance of the process of digestion.
> Option C: Esophagus is a muscular tube which connects the pharynx. The function of esophagus is to transport bolus from pharynx to the stomach. It has no role in chemical digestion.
> Option D: Small intestine is a thin and long tube which is present in the lower gastrointestinal tract. In the small intestine 90% of the digestion takes place. One of the main functions of the small intestine is absorption of minerals and nutrients from food.
> Option E: In large intestine no chemical digestion takes place as there is no presence of digestive enzymes. Therefore, this is the incorrect option.

Thus, the correct answer is option (A) Mouth.

Note: The process of chemical digestion ends in the small intestine and on contrary physical digestion of food takes place from mouth to stomach only.