Year 9 Biology: Chemistry of Food, Organisation and Digestive System

Introduction to the Chemistry of Food

Food is essential for life. It provides us with energy and the nutrients we need to grow and stay healthy. But have you ever wondered what food is made of? The chemistry of food looks at the different substances that make up what we eat. The main components of food are:

1. Carbohydrates: These are our body’s main source of energy. They are found in foods like bread, rice, and potatoes.
2. Proteins: These help build and repair our body tissues. Good sources of protein include meat, fish, eggs, and beans.
3. Fats: Fats provide energy and support cell growth. They can be found in oils, butter, and nuts.
4. Vitamins and Minerals: These are needed in small amounts for various body functions. Fruits and vegetables are great sources of vitamins and minerals.
5. Water: This is vital for life and helps in digestion and nutrient transportation.

Fun Fact:

Did you know that carbohydrates can be simple (like sugar) or complex (like starch)? Simple carbohydrates give quick energy, while complex ones provide lasting energy.

Understanding the Digestive System

Now let’s look at how our body uses food. The digestive system is made up of organs that work together to break down food into smaller parts so our bodies can absorb the nutrients. Here’s how it works:

1. Mouth: Digestion starts here. We chew food, and our saliva begins breaking it down.
2. Oesophagus: This is the tube that carries food from your mouth to your stomach.
3. Stomach: Here, food is mixed with stomach acid and enzymes, which help to break it down further.
4. Small Intestine: Most of the digestion and absorption of nutrients happens here. Enzymes from the pancreas and bile from the liver help digest food.
5. Large Intestine: Water and salts are absorbed here, and the leftover waste is prepared for excretion.
6. Anus: This is where waste leaves the body.

Key Tips for Understanding the Digestive System:

• Visualise: Draw a diagram of the digestive system and label the parts.
• Use Models: Consider using food models or diagrams to show how food moves through the system.
• Relate to Real Life: Think about your own meals and how they go through the digestive system.

Summary

The chemistry of food and the digestive system work hand-in-hand. Food is made of different chemicals, and the digestive system helps us break down those chemicals so we can use them for energy, growth, and repair.

Questions

Easy Level Questions

1. What is the main source of energy for our bodies?
2. Name one type of carbohydrate.
3. What do proteins help our bodies do?
4. Where does digestion start?
5. What is the role of the stomach in digestion?
6. What tube carries food to the stomach?
7. What is the main function of the small intestine?
8. What do vitamins help with?
9. Name a fat-rich food.
10. Where does waste exit the body?
11. What do we call the liquid that helps digest food in the stomach?
12. What organ produces bile?
13. What is the role of saliva in digestion?
14. Name a good source of protein.
15. How does food move through the digestive system?
16. Why is water important for digestion?
17. What do we call the leftover waste in the large intestine?
18. What part of the digestive system absorbs most nutrients?
19. Name one vitamin and its source.
20. What happens in the large intestine?

Medium Level Questions

1. Explain the difference between simple and complex carbohydrates.
2. Describe what happens to food in the stomach.
3. How do enzymes help in digestion?
4. What is the role of the pancreas in digestion?
5. Why is it important to eat a balanced diet?
6. How do fats benefit our bodies?
7. What happens if we don’t get enough water?
8. Name two functions of vitamins.
9. Describe the journey of food from the mouth to the anus.
10. How does the body use the nutrients it absorbs?
11. What is the difference between absorption and digestion?
12. Why is it important for the small intestine to be long and folded?
13. How do we get energy from food?
14. What is the function of the large intestine?
15. Name one type of mineral and its function.
16. What happens to food after it leaves the stomach?
17. Explain how the digestive system is organized.
18. Why do we need to chew our food?
19. What are dietary fibres, and why are they important?
20. How does digestion differ between animals and humans?

Hard Level Questions

1. Explain how enzymes work and give examples of three enzymes involved in digestion.
2. Discuss the role of bile in the digestion of fats.
3. How does the structure of the small intestine aid in nutrient absorption?
4. What is the chemical process of digestion called?
5. Discuss the importance of each organ in the digestive system.
6. Explain how carbohydrates are broken down into sugars.
7. How do nutrients enter the bloodstream from the digestive system?
8. Describe the role of gut bacteria in digestion.
9. What are the consequences of an unhealthy digestive system?
10. Discuss how the body regulates digestion.
11. Explain the significance of each type of macronutrient.
12. How do different diets impact the digestive system?
13. Describe the process of peristalsis.
14. What role does the gallbladder play in digestion?
15. Explain why enzymes are specific to their substrates.
16. How does the digestive system interact with other systems in the body?
17. Discuss the significance of water-soluble and fat-soluble vitamins.
18. What is lactose intolerance, and how does it affect digestion?
19. How does the body adapt to changes in diet?
20. Explain the role of the liver in digestion and metabolism.

Answers

Easy Level Answers

1. Carbohydrates
2. Bread
3. Build and repair tissues
4. Mouth
5. Breaks down food
6. Oesophagus
7. Digestion and absorption
8. Body functions
9. Oils
10. Anus
11. Stomach acid
12. Liver
13. Starts breaking down food
14. Meat
15. Through peristalsis (muscle contractions)
16. Helps with digestion
17. Waste
18. Small intestine
19. Vitamin C from oranges
20. It is removed from the body.

Medium Level Answers

1. Simple carbohydrates are quick energy; complex carbohydrates provide longer-lasting energy.
2. Food is mixed with acid and enzymes to break it down.
3. They speed up the chemical reactions in digestion.
4. The pancreas produces enzymes that help digest carbohydrates, proteins, and fats.
5. To ensure we get all the nutrients we need for health.
6. They provide energy and support cell growth.
7. You may become dehydrated and have digestion problems.
8. Help with immune function and energy production.
9. It passes through the mouth, oesophagus, stomach, small intestine, large intestine, and out of the anus.
10. For energy, growth, and repair.
11. Digestion breaks food down; absorption is taking nutrients into the bloodstream.
12. More surface area for absorption.
13. To help break down food into smaller pieces.
14. To absorb water and form waste.
15. Iron helps carry oxygen in the blood.
16. Each organ has a specific function that aids in digestion.
17. Water-soluble vitamins dissolve in water; fat-soluble vitamins are stored in fat.
18. It means the body can’t digest lactose, leading to discomfort.
19. It can adapt by adjusting enzyme production or gut bacteria.
20. It produces bile, which helps digest fats and filters toxins.

Hard Level Answers

1. Enzymes speed up chemical reactions; e.g., amylase breaks down starch into sugars.
2. Bile emulsifies fats, making them easier to digest.
3. The small intestine has villi and microvilli that increase surface area for absorption.
4. Digestion is called catabolism.
5. Each organ plays a role in breaking down, absorbing, or processing food.
6. Carbohydrates are broken down by enzymes into simple sugars.
7. Nutrients pass through the intestinal walls into the bloodstream.
8. They help break down food and produce certain vitamins.
9. Problems like indigestion, malnutrition, or diseases can occur.
10. The body releases hormones that regulate digestion.
11. Macronutrients are needed for energy, growth, and repair.
12. Different diets can affect gut health and digestion efficiency.
13. Peristalsis is the wave-like motion that moves food through the digestive tract.
14. It stores and releases bile into the small intestine when needed.
15. Each enzyme fits a specific substrate like a key in a lock.
16. The digestive system works with the circulatory system to distribute nutrients.
17. Water-soluble vitamins must be consumed regularly; fat-soluble can be stored.
18. It can lead to gas, bloating, and digestive discomfort.
19. The body can increase enzyme production or adjust gut bacteria.
20. It helps metabolize nutrients and detoxifies harmful substances.