Digestive System Worksheet with Answers (Grade 11 Biology)
A free printable digestive system worksheet for Grade 11 biology.
This free digestive system worksheet follows a meal from the mouth to the rectum. Students label ten organs on a full-colour digestive system diagram, put the organs in the order food passes through them, and sort processes into mechanical and chemical digestion.
They then complete a digestive enzyme table, read an enzyme-pH graph for pepsin and trypsin, interpret classic food tests, and calculate how folds, villi and microvilli multiply the surface area of the small intestine.
- Grade 11 Biology
- 23 marks
- 40–50 minutes
- Full answer key
What's in This Digestive System Worksheet
| Part | Skill practised | Marks |
|---|---|---|
| A | Label the digestive system (10 organs) | 5 |
| B | The journey of food; mechanical vs chemical digestion | 4 |
| C | Digestive enzymes | 3 |
| D | Enzyme activity and pH graph | 3 |
| E | Food tests | 3 |
| F | Absorption and villi surface area | 3 |
| G | Spot the mistake | 2 |
It supports the Ontario Grade 11 biology curriculum expectations in the Animals: Structure and Function unit.
Organs of the Digestive System
1 mouth · 2 salivary gland · 3 esophagus · 4 liver · 5 gallbladder · 6 stomach · 7 pancreas · 8 small intestine · 9 large intestine · 10 rectum
Food travels through the alimentary canal: mouth → esophagus → stomach → small intestine → large intestine → rectum. The liver, gallbladder and pancreas are accessory organs. They add bile and enzymes, but food never passes through them. For more detail, see the human digestive system on Wikipedia.
Mechanical and Chemical Digestion
Mechanical digestion breaks food into smaller pieces: chewing in the mouth and churning in the stomach. Chemical digestion uses enzymes to break large molecules into small ones, such as amylase turning starch into maltose. Part B of the digestive system worksheet asks students to sort four processes into each type.
Digestive Enzymes and pH
| Enzyme | Where it is made | What it digests | Product |
|---|---|---|---|
| Amylase | Salivary glands and pancreas | Starch | Maltose (a sugar) |
| Pepsin | Stomach | Proteins | Peptides |
| Lipase | Pancreas | Fats (lipids) | Fatty acids and glycerol |
Each enzyme has an optimum pH. Pepsin peaks at about pH 2, matching the acidic stomach, while trypsin peaks at about pH 8 in the small intestine. Outside its range an enzyme is denatured: its active site changes shape and it stops working. Since enzymes are proteins, the protein synthesis worksheet shows how cells build them.
Food Tests and Absorption
| Test | Nutrient detected | Positive result |
|---|---|---|
| Iodine solution | Starch | Blue-black |
| Benedict’s solution (heated) | Simple sugars (e.g. glucose) | Orange to brick red |
| Biuret reagent | Protein | Purple |
| Sudan III | Lipids (fats) | Red-stained oily layer |
Once food is digested, the small nutrient molecules are absorbed in the small intestine. Folds, villi and microvilli multiply its surface area: a 10 cm² patch becomes about 6,000 cm². Capillaries in each villus carry the nutrients into the blood, linking this digestive system worksheet to the circulatory system worksheet.
Digestive System Worksheet Practice Questions
These questions match the digestive system worksheet PDF, which has the full-size diagram, word bank and ruled answer space.
Part A – Label the Digestive System
Questions 1–10: label the ten numbered organs in the diagram above.
Part B – The Journey of Food
- Put these organs in the order food passes through them: small intestine, esophagus, mouth, large intestine, stomach, rectum.
- Mechanical or chemical? Chewing food with the teeth.
- Mechanical or chemical? Amylase breaking starch into maltose.
- Mechanical or chemical? Stomach muscles churning food.
- Mechanical or chemical? Pepsin breaking proteins into peptides.
Part C – Digestive Enzymes
Questions 16–18: complete the missing cells for amylase, pepsin and lipase.
Part D – Enzymes and pH
- What is the optimum pH of each enzyme?
- Pepsin works in the stomach. Use the graph to explain why it is suited to that organ.
- Why does pepsin stop working when it reaches the small intestine (about pH 8)?
Part E – Food Tests
Questions 22–25: name the nutrient each test detects and its positive result. Question 26: interpret a set of food test results.
Part F – Absorption
- Explain how villi help the small intestine absorb nutrients.
- A smooth section of small intestine would have a surface area of 10 cm². Folds multiply the area by 3, villi by 10 and microvilli by 20. Calculate the actual surface area. (2 marks)
Part G – Spot the Mistake
- A student writes: “Digestion starts in the stomach.” Explain the error and correct it.
- A student writes: “Bile is an enzyme that breaks down fats.” Explain the error and correct it.
Digestive System Worksheet Answer Key
Open each part of the digestive system worksheet answers to check your work. The printable key is at the end of the PDF.
Part A answers (Q1–10)
- Mouth
- Salivary gland
- Esophagus
- Liver
- Gallbladder
- Stomach
- Pancreas
- Small intestine
- Large intestine
- Rectum
Part B answers (Q11–15)
- R → Q → T → P → S → U (mouth → esophagus → stomach → small intestine → large intestine → rectum)
- Mechanical
- Chemical
- Mechanical
- Chemical
Part C answers (Q16–18)
- Amylase: made in salivary glands and pancreas; digests starch; product maltose (a sugar)
- Pepsin: made in stomach; digests proteins; product peptides
- Lipase: made in pancreas; digests fats (lipids); product fatty acids and glycerol
Part D answers (Q19–21)
- Pepsin: pH 2; trypsin: pH 8
- The stomach is very acidic (about pH 2) because of hydrochloric acid, which matches pepsin’s optimum.
- The high pH changes the shape of its active site (it is denatured), so it can no longer bind its substrate.
Part E answers (Q22–26)
- Iodine solution: Starch, blue-black
- Benedict’s solution (heated): Simple sugars (e.g. glucose), orange to brick red
- Biuret reagent: Protein, purple
- Sudan III: Lipids (fats), red-stained oily layer
- Starch and protein, but no simple sugars
Part F answers (Q27–28)
- They give a huge surface area, have walls only one cell thick, and contain capillaries (and lacteals) to carry nutrients away.
- 10 × 3 × 10 × 20 = 6,000 cm² (600 times larger)
Part G answers (Q29–30)
- Digestion starts in the mouth: teeth break food up (mechanical) and salivary amylase starts digesting starch (chemical).
- Bile is not an enzyme. It emulsifies fats into small droplets; the enzyme lipase then digests them.
5 Common Digestive System Mistakes
- "Digestion starts in the stomach." It starts in the mouth, with chewing and salivary amylase.
- Calling bile an enzyme. Bile emulsifies fats; lipase digests them.
- Sending food through the liver or pancreas. These accessory organs never carry food.
- Saying high temperature or pH "kills" enzymes. Enzymes aren't alive; they are denatured.
- Forgetting to heat Benedict's solution. The colour change only happens in a hot water bath.
How to Use This Digestive System Worksheet in Class
- Lesson 1: Parts A–C of the digestive system worksheet, starting by tracing a cracker from mouth to rectum.
- Lesson 2: Parts D–G, ideally alongside a food-testing lab with iodine, Benedict's and Biuret.
- Extension: Students research how lactose intolerance or celiac disease affects digestion.
Review with the digestive system quiz and the macromolecules quiz.
Frequently Asked Questions
Is this digestive system worksheet free?
Yes. The worksheet and its answer key are free to download and print as a PDF, with no account needed.
What is the order of organs in the digestive system?
Food travels from the mouth to the esophagus, stomach, small intestine, large intestine and rectum. The liver, gallbladder and pancreas help with digestion, but food does not pass through them.
What is the difference between mechanical and chemical digestion?
Mechanical digestion physically breaks food into smaller pieces, as in chewing and churning. Chemical digestion uses enzymes to break large molecules into small ones the body can absorb.
Why do different digestive enzymes work at different pH levels?
Each enzyme's shape works best at a particular pH. Pepsin is suited to the acidic stomach (about pH 2), while trypsin and pancreatic enzymes work in the slightly basic small intestine (about pH 8).
Where are most nutrients absorbed?
In the small intestine. Folds, villi and microvilli give it an enormous surface area, and each villus has capillaries that carry nutrients into the blood.
More Free Grade 11 Biology Resources
Ready to start? Download the free digestive system worksheet PDF (use the Download button above), print it double-sided, and keep the answer key pages for marking.