O Level Biology: Human Nutrition Questions and Answers

O Level Biology Questions and Answers

Subject: Biology

Level: O Level

Topic: Human Nutrition

This resource provides a complete set of O Level Biology Questions and Answers on human nutrition – how the body obtains and processes food for energy, growth, and health. You will explore the components of a balanced diet, the structure and function of the digestive system, the role of enzymes in digestion, and the causes and effects of malnutrition. Perfect for mastering these essential concepts.

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Topic Overview

Human nutrition involves the intake of food and its breakdown into usable nutrients. A balanced diet includes carbohydrates, proteins, fats, vitamins, minerals, fibre, and water. The digestive system breaks down large food molecules into smaller, soluble molecules that can be absorbed into the bloodstream. Digestion involves mechanical (teeth, stomach churning) and chemical (enzymes) processes. Organs include the mouth, oesophagus, stomach, small intestine, large intestine, liver, and pancreas. Malnutrition can result from deficiencies (e.g., scurvy, anaemia) or excesses (e.g., obesity). Understanding these processes is fundamental to human health and disease prevention.

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Exam Questions and Answers

Question 1

Question:
What are the seven components of a balanced diet? Give one function of each.

Answer:
1. Carbohydrates – energy source.
2. Proteins – growth and repair of tissues.
3. Fats – energy store and insulation.
4. Vitamins – required for specific metabolic processes (e.g., vitamin C for connective tissue).
5. Minerals – essential for various functions (e.g., calcium for bones).
6. Fibre (roughage) – helps move food through the gut, preventing constipation.
7. Water – solvent, transport, and temperature regulation.

Explanation:
A balanced diet provides all nutrients in correct proportions. Lack of any can lead to deficiency diseases. Excess can cause obesity or other disorders.

Exam Tip:
Learn one specific function for each. For vitamins and minerals, mention specific examples (e.g., vitamin C prevents scurvy; iron prevents anaemia).

Question 2

Question:
Describe the role of enzymes in digestion.

Answer:
Enzymes are biological catalysts that speed up the breakdown of large, insoluble food molecules into smaller, soluble molecules that can be absorbed. Amylase breaks down starch into maltose; protease breaks down proteins into amino acids; lipase breaks down fats into fatty acids and glycerol.

Explanation:
Digestive enzymes are produced in the salivary glands, stomach, pancreas, and small intestine. They are specific to their substrates and work at optimum pH (e.g., pepsin in acidic stomach, trypsin in alkaline small intestine).

Exam Tip:
Know where each enzyme is produced and where it acts. Use “specificity” and “optimum pH” in answers.

Question 3

Question:
List the organs of the alimentary canal in order from mouth to anus.

Answer:
Mouth → oesophagus → stomach → small intestine (duodenum and ileum) → large intestine (colon and rectum) → anus.

Explanation:
The alimentary canal is a continuous tube where food passes. Associated glands (salivary glands, liver, pancreas) secrete digestive juices into it.

Exam Tip:
Memorise the sequence. Include “duodenum” and “ileum” as parts of the small intestine, and “colon” and “rectum” as parts of the large intestine.

Question 4

Question:
Explain how the small intestine is adapted for absorption of digested food.

Answer:
The small intestine has villi and microvilli that greatly increase surface area for absorption. Each villus contains a network of capillaries (for absorbing amino acids and sugars) and a lacteal (for absorbing fatty acids and glycerol). The wall is thin, allowing rapid diffusion. It also has a rich blood supply to maintain a concentration gradient.

Explanation:
Villi are finger‑like projections. Microvilli are tiny folds on their surface. These adaptations ensure efficient uptake of nutrients into the bloodstream and lymphatic system.

Exam Tip:
Mention “villi”, “microvilli”, “large surface area”, “rich blood supply”, and “lacteal”. Link structure to function.

Question 5

Question:
What is the function of bile in digestion? Where is it produced and stored?

Answer:
Bile emulsifies fats (breaks large fat droplets into smaller ones), increasing surface area for lipase action. It also neutralizes stomach acid, providing an alkaline pH for pancreatic enzymes. Bile is produced in the liver and stored in the gallbladder.

Explanation:
Emulsification is physical, not chemical. Bile does not contain enzymes. It is released into the duodenum when fatty food enters.

Exam Tip:
Use the term “emulsify”. Distinguish between bile salts (emulsification) and enzyme action (chemical).

Question 6

Question:
Describe the process of chemical digestion of starch in the human digestive system.

Answer:
Starch digestion begins in the mouth with salivary amylase, which breaks starch into maltose. In the small intestine, pancreatic amylase continues the breakdown. Maltose is then broken down into glucose by maltase (on the intestinal lining).

Explanation:
Salivary amylase works best at neutral pH. Pancreatic amylase works in the alkaline environment of the duodenum. The final product, glucose, is absorbed into the blood.

Exam Tip:
Name the enzymes and where they act. Include “maltose” as intermediate and “glucose” as final product.

Question 7

Question:
What are the deficiency symptoms of vitamin C and iron?

Answer:
Vitamin C deficiency causes scurvy (bleeding gums, poor wound healing). Iron deficiency causes anaemia (tiredness, pale skin, shortness of breath) because iron is needed to make haemoglobin in red blood cells.

Explanation:
Vitamin C is needed for collagen production. Iron is a component of haemoglobin. Lack of these leads to specific health problems.

Exam Tip:
Be precise: “scurvy” for vitamin C, “anaemia” for iron. You may also mention sources (citrus fruits for vitamin C; red meat, spinach for iron).

Question 8

Question:
Explain how the stomach is adapted for its role in digestion.

Answer:
The stomach has a thick muscular wall that churns food (mechanical digestion). Its inner lining secretes gastric juice containing hydrochloric acid (HCl) and pepsinogen (activated to pepsin). HCl provides an acidic pH for pepsin to work, kills bacteria, and denatures proteins. Pepsin breaks down proteins into polypeptides.

Explanation:
The acidic environment also protects against pathogens. The stomach’s mucus layer prevents self‑digestion.

Exam Tip:
Mention both mechanical (churning) and chemical (gastric juice, pepsin, HCl) digestion. Include the importance of pH and mucus.

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Key Concepts Summary

• Balanced diet: carbohydrates, proteins, fats, vitamins, minerals, fibre, water.
• Digestive system: mouth, oesophagus, stomach, small intestine, large intestine, anus; accessory organs: liver, gallbladder, pancreas.
• Digestive enzymes: amylase (starch → maltose), protease (protein → amino acids), lipase (fats → fatty acids + glycerol).
• Absorption occurs mainly in small intestine via villi (large surface area, rich blood supply, lacteals).
• Bile emulsifies fats and neutralizes acid; produced in liver, stored in gallbladder.
• Deficiency diseases: scurvy (vitamin C), anaemia (iron), rickets (vitamin D/calcium), beriberi (vitamin B1).

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Frequently Asked Questions

What is the difference between mechanical and chemical digestion?

Mechanical digestion physically breaks food into smaller pieces (e.g., chewing, stomach churning). Chemical digestion uses enzymes to break down large molecules into smaller, soluble ones (e.g., amylase breaking starch into sugar).

Why is fibre important even though it is not digested?

Fibre adds bulk to food, helps peristalsis, and prevents constipation by keeping the contents of the large intestine moving. It may also reduce the risk of bowel disorders.

How does the body regulate blood glucose after a meal?

After a meal, blood glucose rises. The pancreas releases insulin, which stimulates cells to take up glucose and store it as glycogen in the liver and muscles, lowering blood glucose back to normal.

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Related Topics

• O Level Biology Biological Molecules Questions and Answers Live 
• O Level Biology Enzymes Questions and Answers live
• O Level Biology Transport in Humans Questions and Answers Live 

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Conclusion

Mastering O Level Biology Questions and Answers on human nutrition gives you a solid understanding of how the body processes food and the importance of a balanced diet. Learn the roles of each nutrient, the path of food through the digestive system, and the actions of enzymes and bile. Practice these questions, review the key concepts, and use the exam tips to succeed in your exams.