Chemical digestion occurs when acids, enzymes and other secretions break down the food we eat into nutrients. Chemical digestion starts in the mouth and continues in the stomach, but most of the process occurs in the small intestine.
Chemical digestion differs from mechanical digestion, which occurs in the mouth as the teeth grind and chew pieces of food. Some mechanical digestion also takes place in the stomach as the muscles churn food particles.
Chemical digestion begins in the mouth. The enzyme amylase, found in saliva, starts breaking down carbohydrates.
Chemical digestion continues in the stomach. Hydrochloric acid and the enzyme pepsin work on digesting proteins.
A cocktail of enzymes in the small intestine completes the chemical digestion process. Most chemical digestion takes place in the duodenum portion of the small intestine.
Chemical digestion breaks down carbohydrates, proteins and fats into sugars, amino acids and fatty acids that the body can absorb and use as fuel.