Enzymes in digestion
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of the structure and function of biological molecules such as starch, proteins, and lipids and the general function of the digestive system.
What are the three main types of biological molecules found in food?
Carbohydrates, proteins, and lipids.
What is the function of the digestive system?
To break down large, insoluble food molecules into small, soluble ones that can be absorbed.
What is an organ system?
A group of organs working together to carry out a particular function.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains enzymes in digestion, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
What Are Digestive Enzymes?
Digestive enzymes are biological catalysts that speed up the breakdown of large food molecules into smaller, soluble ones that can be absorbed into the blood.
Key Enzyme Types and Their Functions
|
Enzyme |
Substrate |
Product(s) |
Site of Production |
Site of Action |
|
|
Amylase |
Starch (Carbohydrate) |
→ |
Simple sugars (glucose, maltose) |
Salivary glands, pancreas, small intestine |
Mouth, small intestine |
|
Protease |
Protein |
→ |
Amino acids |
Stomach, pancreas, small intestine |
Stomach, small intestine |
|
Lipase |
Lipids (fats) |
→ |
Glycerol + fatty acids |
Pancreas, small intestine |
Small intestine |
Enzymes are specific because of the shape of their active site - they only work with one type of substrate.
Use of Digestion Products
-
Glucose: used for respiration to release energy. Used for making new carbohydrates such as glycogen which is stored in the liver and muscles.
-
Amino acids: used to build new proteins (protein synthesis).
-
Fatty acids & glycerol: used to make new lipids (lipid synthesis) such as lipids needed in cell membranes.
Key Terms
- Enzyme – a biological catalyst that speeds up reactions.
- Substrate – the molecule an enzyme acts on.
- Active Site - Part of the enzyme where the substrate binds.
No answer provided.
Exam Tip
In questions asking for enzyme action, always include:
- the enzyme name
- the substrate
- and the products
No answer provided.
Practice Question
Describe how proteins are broken down in the digestive system and state where this happens. (4 marks)
-
Proteins are broken down by enzymes called proteases.
-
Proteases break down proteins into amino acids.
-
Proteases are produced in the stomach, pancreas and small intestine.
-
They work in the stomach and small intestine.
Note - food does not go into the pancreas! The pancreas releases the enzymes it produces into the small intestine.
More Practice
Try to answer these practice questions from the TikTok videos on your own, then watch the videos to see how well you did!