What is Digestion and How Do Digestive Enzymes Work?
Digestion is the process of breaking down food into smaller molecules the body can absorb and use for energy. Digestive enzymes are biological catalysts that speed up this breakdown, each targeting a specific type of nutrient — carbohydrates, proteins, or fats. Together, mechanical and chemical digestion turn a meal into usable building blocks for the body.
Digestion breaks food into absorbable nutrients using digestive enzymes such as amylase (carbohydrates), pepsin (proteins), and lipase (fats), each working best in a specific part of the digestive tract.
- 1↓MouthChewing plus salivary amylase begins breaking down starch
- 2↓StomachPepsin and stomach acid break down proteins
- 3↓Small IntestinePancreatic amylase, lipase and trypsin digest carbs, fats and proteins
- 4AbsorptionNutrient molecules pass through the intestinal wall into the bloodstream
Step-by-step worked examples
A slice of bread contains starch. Which enzyme starts breaking it down, and where?
Starch is a carbohydrate Salivary amylase begins breaking it into smaller sugars in the mouth
A piece of chicken (protein) is eaten. Which enzyme breaks it down, and where?
Protein digestion starts in the stomach Pepsin, activated by stomach acid (HCl), breaks proteins into smaller peptides
A meal contains 60 g of fat. Which enzyme digests it, and what does it produce?
Fats are digested mainly in the small intestine Lipase (helped by bile) breaks fat into fatty acids and glycerol for absorption
Flashcards
Quick quiz
Q1.Which enzyme breaks down starch?
Q2.Where does protein digestion mainly begin?
Q3.What does lipase break fats into?
Q4.What helps activate pepsin in the stomach?
The full card deck, worked steps and AI-tutor support for “What is Digestion and How Do Digestive Enzymes Work?” are in Notek — study by hand before your exam.
Common mistakes
Thinking all digestion happens in the stomach. — Correct: Digestion starts in the mouth and is completed mostly in the small intestine.
Confusing bile with an enzyme. — Correct: Bile is not an enzyme — it emulsifies fat so lipase can work more effectively.
Believing amylase digests protein. — Correct: Amylase digests carbohydrates/starch, not protein.
Assuming absorption happens in the stomach. — Correct: Most nutrient absorption happens in the small intestine, not the stomach.
FAQ
What are digestive enzymes?
Proteins that speed up the breakdown of food into absorbable nutrients, such as amylase, pepsin and lipase.
How does digestion work step by step?
Food is broken down mechanically and chemically from the mouth through the stomach to the small intestine, where nutrients are absorbed.
What are examples of digestive enzymes?
Amylase (carbs), pepsin (protein), lipase (fats) and trypsin (protein) are common examples.
How is digestion different from absorption?
Digestion breaks food down into smaller molecules; absorption is when those molecules pass into the bloodstream.