Introduction to Digestion

Digestion is the process by which the body breaks down food into smaller molecules that can be absorbed into the bloodstream and used by the body for energy, growth, and repair. Digestion occurs in the digestive system, which consists of a series of organs that work together to break down food.

Key Stages of Digestion

1. Ingestion: Taking in food through the mouth.
2. Mechanical Digestion: Physical breakdown of food, like chewing, to increase its surface area.
3. Chemical Digestion: Enzymes and acids break down complex molecules in food into simpler forms.
4. Absorption: The small, broken-down molecules pass through the walls of the small intestine into the bloodstream.
5. Egestion: Removal of undigested waste from the body.

Main Organs Involved in Digestion

1. Mouth: Where digestion begins with chewing and saliva, which contains enzymes to start breaking down carbohydrates.
2. Oesophagus: A muscular tube that pushes food from the mouth to the stomach through a process called peristalsis.
3. Stomach: Uses acid and enzymes to continue breaking down food.
4. Small Intestine: Where most digestion and absorption of nutrients occurs, assisted by enzymes from the pancreas and bile from the liver.
5. Large Intestine: Absorbs water and forms waste, which is then expelled from the body.

Understanding digestion is essential to appreciate how our bodies process and benefit from the food we eat.

Exam Questions on Digestion

To test your understanding of the topic, here are 20 questions each at easy, medium, and hard levels.

Easy Level Questions

Basic Understanding of Digestion

1. What is digestion?
2. What is the first stage of digestion called?
3. What type of digestion involves chewing food?
4. What is the role of the stomach in digestion?
5. What organ connects the mouth to the stomach?
6. What is the main purpose of digestion?
7. Where does digestion begin in the body?
8. What type of acid is found in the stomach?
9. What is the role of saliva in digestion?
10. What is the name of the long tube in the digestive system?
11. What is peristalsis?
12. What is the function of enzymes in digestion?
13. Where does most nutrient absorption occur?
14. What is the name of the organ where water is absorbed?
15. What does the term ‘egestion’ mean?
16. What are nutrients?
17. Which organ stores bile?
18. What does bile help to digest?
19. Where is bile produced?
20. What does the large intestine do with water?

Medium Level Questions

Intermediate Knowledge of the Digestive Process

1. Explain the difference between mechanical and chemical digestion.
2. Describe the role of the small intestine in digestion.
3. What is the purpose of enzymes in the digestive system?
4. How does chewing help with digestion?
5. What is the role of the pancreas in digestion?
6. Name the enzyme found in saliva and its function.
7. What does the liver produce to aid in digestion?
8. How does the stomach protect itself from acid?
9. What are villi and where are they found?
10. Explain why peristalsis is important in digestion.
11. What does amylase break down?
12. What are proteins broken down into during digestion?
13. Describe one function of the large intestine.
14. How does the body use the nutrients absorbed during digestion?
15. What type of nutrient does lipase break down?
16. Where does protein digestion primarily occur?
17. Explain why enzymes are important for chemical digestion.
18. Describe how bile aids in digestion.
19. What is the role of mucus in the digestive system?
20. Where does food go after it leaves the stomach?

Hard Level Questions

Advanced Concepts and Applications in Digestion

1. Explain how enzymes speed up digestion.
2. Describe the role of hydrochloric acid in the stomach.
3. Explain how bile helps to emulsify fats.
4. How are carbohydrates, fats, and proteins different in terms of digestion?
5. Describe the relationship between the liver and the gallbladder in digestion.
6. What is the role of the small intestine’s villi in nutrient absorption?
7. Explain why the surface area of the small intestine is so important.
8. How does the body control the release of digestive enzymes?
9. Describe how the structure of villi aids in their function.
10. Explain why the stomach doesn’t digest itself.
11. How does the digestive system prevent harmful bacteria from entering the bloodstream?
12. What are the end products of carbohydrate digestion?
13. Describe how absorbed nutrients are transported around the body.
14. Explain the difference between absorption and assimilation.
15. How does the body regulate the pH of the small intestine?
16. Describe the role of lactase and where it functions.
17. Why is fibre important for the digestive system, even though it isn’t digested?
18. Explain how the pancreas regulates blood sugar.
19. What is the relationship between diet and enzyme efficiency in digestion?
20. Describe how the body deals with undigested material.

Answers and Explanations

Easy Level Answers

1. The process of breaking down food – Digestion converts food into smaller molecules the body can use.
2. Ingestion – The first stage of digestion involves taking in food.
3. Mechanical digestion – Chewing is an example of mechanical digestion.
4. Uses acid and enzymes to break down food – The stomach helps digest food into smaller pieces.
5. Oesophagus – The oesophagus connects the mouth to the stomach.
6. To break down food for energy and growth – Digestion allows the body to use nutrients.
7. Mouth – Digestion begins with chewing in the mouth.
8. Hydrochloric acid – This acid helps break down food in the stomach.
9. Moistens food and contains enzymes – Saliva helps break down food and begins digestion.
10. Digestive tract or alimentary canal – A long tube that food travels through.
11. A muscular movement that pushes food down – Peristalsis helps food move through the oesophagus.
12. To speed up the breakdown of food – Enzymes assist chemical digestion.
13. Small intestine – Most nutrients are absorbed in the small intestine.
14. Large intestine – This organ absorbs water.
15. Removal of undigested waste – Egestion is the process of removing waste.
16. Substances the body needs to function – Nutrients are absorbed to help the body work.
17. Gallbladder – Bile is stored in the gallbladder.
18. Fats – Bile helps break down fats into smaller pieces.
19. Liver – The liver produces bile.
20. Absorbs it – The large intestine absorbs water from waste.

Medium Level Answers

1. Mechanical digestion is physical (like chewing); chemical digestion uses enzymes and acids.
2. Absorbs nutrients and completes digestion – The small intestine digests and absorbs nutrients.
3. Break down food molecules – Enzymes help turn complex molecules into simpler ones.
4. Increases surface area of food for enzymes – Chewing aids in digestion by making food easier to break down.
5. Produces enzymes to break down food – The pancreas releases enzymes for digestion.
6. Amylase; it breaks down carbohydrates – Amylase in saliva helps digest starch.
7. Bile – The liver produces bile, which aids in fat digestion.
8. A thick mucus layer – Mucus protects the stomach lining from acid.
9. Finger-like structures in the small intestine – Villi increase surface area for absorption.
10. Moves food through the digestive system – Peristalsis helps push food along the tract.
11. Starch – Amylase breaks down starch into simpler sugars.
12. Amino acids – Proteins are broken down into amino acids.
13. Absorbs water and forms waste – The large intestine absorbs water.
14. Used for energy, growth, and repair – Nutrients from digestion fuel the body.
15. Fats – Lipase breaks down fats into fatty acids and glycerol.
16. Stomach and small intestine – Protein digestion starts in the stomach.
17. They speed up reactions, helping digest food – Enzymes are crucial for efficient digestion.
18. Breaks fats into small droplets – Bile helps fats mix with digestive enzymes.
19. Protects and lubricates – Mucus lines the digestive tract.
20. Small intestine – Food moves to the small intestine after the stomach.

Hard Level Answers

1. Enzymes lower activation energy, making digestion faster.
2. **Hydrochloric acid kills bacteria and activates enzymes** – It creates an acidic environment in the stomach.
3. Bile breaks down fats into tiny droplets – Emulsification allows enzymes to work better on fats.
4. Carbohydrates break into sugars, fats into fatty acids, proteins into amino acids.
5. The liver produces bile, stored in the gallbladder until needed.
6. Villi have a large surface area for efficient nutrient absorption.
7. Increased surface area allows more nutrients to be absorbed.
8. Enzymes are released based on the presence of food – The body adjusts enzyme levels as needed.
9. Finger-like projections increase surface area for faster absorption.
10. A thick mucus layer and rapid cell turnover protect the stomach lining.
11. Acid and enzymes kill bacteria – The stomach and intestines prevent bacteria from entering the blood.
12. Simple sugars (like glucose) – Carbohydrates are digested into sugars.
13. Nutrients enter the bloodstream and are transported to cells.
14. Absorption is taking in nutrients; assimilation is using them in the body.
15. The pancreas releases bicarbonate – This neutralises stomach acid in the small intestine.
16. Lactase breaks down lactose in the small intestine.
17. Fibre helps keep the digestive system moving smoothly.
18. The pancreas also releases insulin to regulate blood sugar levels.
19. A balanced diet ensures enzymes work effectively.
20. Undigested material is formed into waste and removed from the body.

This set of questions and answers gives Year 8 students a comprehensive understanding of the digestive system, equipping them for their Key Stage 3 exams.