Digestion Process
Elementary School
Definition
The breakdown of food into smaller molecules that the body can absorb and use. It begins in the mouth and continues in the stomach and intestines, where mechanical action and enzymes turn food into nutrients.
Worked examples
Mouth: teeth break down a cracker into smaller pieces while saliva enzymes begin breaking down starches into sugars.
Mechanical and chemical digestion both start in the mouth.
Stomach: churning muscle action mixes food with acid and pepsin enzyme, turning a piece of chicken into a thick liquid (chyme).
The stomach uses both physical breakdown and enzymes to digest proteins.
Small intestine: enzymes from the pancreas finish breaking down fats, carbohydrates, and proteins so tiny nutrient molecules can pass into the blood.
Most chemical digestion and all nutrient absorption happen in the small intestine.
Common mistakes
- Digestion only happens in the stomach. → Digestion begins in the mouth and continues through the stomach and intestines. Each organ plays a role; the stomach is just one step in the process.
- Digestion and absorption are the same thing. → Digestion breaks down food; absorption moves nutrients into the bloodstream. Digestion prepares food so absorption can happen.
- Enzymes in the stomach break down all types of food equally. → Different enzymes target specific nutrients (pepsin for proteins, lipase for fats, amylase for carbs). Each enzyme is specialized for one type of molecule.
Where you'll use it next
You'll apply the digestion process when studying cellular respiration (how cells use glucose), nutrient absorption and the circulatory system, and disorders like lactose intolerance or celiac disease in health science.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026