What is the importance of a balanced diet in animal nutrition according to the Cambridge IGCSE Coordinated Science curriculum?

A balanced diet is crucial in animal nutrition as it provides all the essential nutrients in the correct proportions needed for growth, energy, and overall health. According to the Cambridge IGCSE Coordinated Science curriculum, a balanced diet includes carbohydrates, proteins, fats, vitamins, minerals, water, and fiber. Each of these components plays a specific role, such as energy provision, tissue repair, and metabolic regulation.

How do carbohydrates function in the diet of animals?

Carbohydrates are a primary source of energy for animals. They are broken down into glucose, which is used by cells to produce ATP, the energy currency of the cell. In the context of the Cambridge IGCSE Coordinated Science curriculum, understanding the role of carbohydrates helps students appreciate how animals meet their energy needs and maintain bodily functions.

Why are proteins essential in an animal's diet?

Proteins are essential in an animal's diet because they are the building blocks of body tissues and are vital for growth and repair. They are made up of amino acids, some of which are essential and must be obtained through diet. The Cambridge IGCSE Coordinated Science curriculum highlights the importance of proteins in enzyme production, hormone regulation, and immune function.

What role do vitamins and minerals play in animal nutrition?

Vitamins and minerals are crucial for maintaining health and supporting various physiological functions in animals. Vitamins are organic compounds that aid in processes such as vision, bone health, and blood clotting, while minerals like calcium and iron are important for bone structure and oxygen transport, respectively. The Cambridge IGCSE Coordinated Science curriculum emphasizes their role in preventing deficiencies and supporting metabolic processes.

How does fiber contribute to an animal's diet, and why is it important?

Fiber is important in an animal's diet as it aids in digestion and helps maintain a healthy digestive system. It adds bulk to the diet, which facilitates the movement of food through the digestive tract and prevents constipation. The Cambridge IGCSE Coordinated Science curriculum recognizes fiber's role in promoting gut health and preventing digestive disorders.

Why is "Stating that proteins are used only for energy" a common mistake in Diet?

Why it happens: Students associate food with energy and apply this to all macronutrients. How to avoid it: Proteins are primarily used for **growth and repair** of cells. They are an energy source only when other sources are depleted.

Why is "Saying vitamins provide energy" a common mistake in Diet?

Why it happens: Students lump vitamins in with energy-providing nutrients. How to avoid it: Vitamins do NOT provide energy. They are needed in small amounts for specific metabolic functions (e.g. vitamin C for collagen synthesis, vitamin D for calcium absorption).

Why is "Stating all fats are unhealthy and should be avoided" a common mistake in Diet?

Why it happens: Media messages about diet oversimplify the role of lipids. How to avoid it: Lipids are essential for energy storage, cell membrane structure, hormone production, and fat-soluble vitamins (A, D, E, K). Only excessive saturated fats are linked to health risks.

Why is "Classifying dietary fibre as a nutrient that is digested and absorbed" a common mistake in Diet?

Why it happens: Students list fibre alongside carbohydrates and assume it is digested. How to avoid it: Dietary fibre (cellulose) cannot be digested by humans — we lack cellulase. Its role is to add bulk and stimulate peristalsis.

Animal NutritionCambridge IGCSE Coordinated Sciences 0654

Diet

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Diet — Cambridge IGCSE Coordinated Science 0654

A balanced diet contains the right amounts of all seven dietary components. Malnutrition (too little or too much of any component) causes specific, testable health problems. Students frequently confuse the function of different nutrients.

What you’ll learn

Mapped to the Cambridge IGCSE 0654 syllabus (2025-2027).

B7.1 — Describe the components of a balanced diet and their roles.
B7.1 — State the consequences of dietary deficiencies.
B7.1 — Describe malnutrition and its effects.

The Seven Dietary Components — Functions and Deficiencies

Each component has specific roles. Know at least one function and one deficiency per component.

Component	Main Function(s)	Deficiency Consequences
Carbohydrates	Primary energy source; dietary fibre (from complex carbs)	Fatigue; weight loss; ketosis (extreme deficiency)
Proteins	Growth, repair, enzyme synthesis, hormones, antibodies	Kwashiorkor (protein-energy malnutrition) — muscle wasting, oedema, stunted growth
Lipids (fats/oils)	Energy storage; cell membranes; insulation; fat-soluble vitamins (A, D, E, K)	Deficiency of fat-soluble vitamins; energy shortage
Vitamin C	Synthesis of collagen (connective tissue); wound healing; antioxidant	Scurvy — bleeding gums, skin haemorrhages, poor wound healing
Vitamin D	Absorption of calcium and phosphorus; bone mineralisation	Rickets (children — bones don't harden) / Osteomalacia (adults)
Iron	Component of haemoglobin (carries O₂ in red blood cells)	Anaemia — fatigue, pale skin, breathlessness
Calcium	Bone and teeth mineralisation; muscle contraction; nerve impulse	Weak bones, osteoporosis, poor teeth
Water	Solvent for reactions; transport; temperature regulation; excretion	Dehydration — affects all cellular processes
Dietary fibre	Provides bulk to food — stimulates peristalsis (gut movement)	Constipation; increased risk of bowel cancer

Malnutrition = unbalanced diet (too much OR too little of any component):

Undernutrition: inadequate energy intake → underweight, kwashiorkor
Overnutrition: excess energy (especially fat/sugar) → obesity → increased risk of type 2 diabetes, cardiovascular disease, hypertension

Vitamin C → collagen synthesis. Deficiency → scurvy.
Vitamin D → calcium absorption. Deficiency → rickets.
Iron → haemoglobin. Deficiency → anaemia.
Dietary fibre → peristalsis. Deficiency → constipation.
Protein deficiency in children → kwashiorkor (muscle wasting, oedema).

How it’s examined

Paper 2: multiple choice on nutrient functions or deficiency symptoms. Paper 4: 'State the role of iron in the diet and describe the effect of iron deficiency' (2–3 marks). Table-completion on dietary components. Expect the exam to link iron → haemoglobin → oxygen transport → anaemia in a chain.

Sources: Cambridge IGCSE Coordinated Sciences 0654 syllabus 2025-2027 (B7). Last reviewed 2026-05-14.

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Step-by-step worked examples — Diet

Step-by-step solutions to past-paper-style questions on diet, written exactly the way a tutor would explain them at the board.

1State the role of iron in the body
Core• minerals, iron, haemoglobin
Question
State the role of iron in the body.
Step-by-step solution
1. Step 1
  Iron is a component of haemoglobin, the protein in red blood cells.
2. Step 2
  Haemoglobin binds oxygen in the lungs and transports it to body tissues.
Answer
Iron is a component of haemoglobin in red blood cells; haemoglobin transports oxygen around the body. Deficiency causes anaemia (reduced oxygen-carrying capacity).
2Why a pregnant woman needs more protein
Extended• protein, pregnancy, energy requirements
Question
Explain why a pregnant woman requires more protein in her diet than a non-pregnant woman of similar age.
Step-by-step solution
1. Step 1
  Protein is required for growth and repair of cells. During pregnancy, the fetus is growing rapidly and needs protein for new cell formation.
2. Step 2
  Protein is also needed for the growth and maintenance of the placenta, for the increased blood volume and for the developing uterus muscle.
3. Step 3
  Therefore total protein demand is significantly higher during pregnancy to support both maternal and fetal needs.
Answer
A pregnant woman needs more protein because protein is required for: growth of the fetus, development of the placenta, and increased maternal blood volume and uterine muscle. All involve new cell synthesis requiring protein.
3Health risk of a diet high in saturated fat
Extended• lipids, saturated fat, cardiovascular disease
Question
A teenager's diet is high in saturated fat. Explain ONE health risk associated with this diet.
Step-by-step solution
1. Step 1
  Saturated fats raise the level of LDL cholesterol in the blood.
2. Step 2
  Cholesterol can be deposited in artery walls, forming atherosclerotic plaques (atherosclerosis). This narrows the artery lumen and reduces blood flow.
3. Step 3
  If a coronary artery is affected, blood supply to the heart muscle is reduced, increasing the risk of a heart attack (coronary heart disease). High blood pressure can also result.
Answer
A diet high in saturated fat raises blood cholesterol, leading to fatty deposits (atherosclerosis) in artery walls. This narrows arteries and increases the risk of coronary heart disease (heart attack) or stroke.
4Symptoms and cause of scurvy
Core• vitamins, vitamin C, deficiency
Question
State the symptoms of scurvy and identify its dietary cause.
Step-by-step solution
1. Step 1
  Scurvy is caused by a deficiency of vitamin C (ascorbic acid) in the diet.
2. Step 2
  Vitamin C is needed for the synthesis of collagen, a structural protein in connective tissue. Without sufficient collagen, blood vessels become fragile.
3. Step 3
  Symptoms: bleeding gums, loose teeth, poor wound healing, bruising, joint pain.
Answer
Scurvy is caused by a lack of vitamin C in the diet. Symptoms include bleeding gums, poor wound healing, and bruising (due to weakened blood vessels from impaired collagen synthesis).
5Why an athlete needs more carbohydrate than an office worker
Extended• carbohydrate, energy, exercise
Question
Explain why an athlete needs more carbohydrate in their diet than an office worker.
Step-by-step solution
1. Step 1
  Muscles contract during exercise, requiring energy released by aerobic respiration (and anaerobic at high intensity).
2. Step 2
  Carbohydrates (glucose) are the primary and most efficiently used substrate for respiration. More exercise = more respiration = more glucose needed.
3. Step 3
  An office worker has a lower activity level → lower energy expenditure → requires less carbohydrate.
Answer
Athletes have higher energy demands due to increased muscle activity; carbohydrates are the primary fuel for aerobic respiration. Greater physical activity requires more carbohydrate to supply glucose for respiration.

Key Definitions and Keywords — Diet

Definitions to memorise and the exact keywords mark schemes credit for diet answers — sharpened from recent examiner reports for the 2026 0654 sitting.

Balanced diet
Examiner keyword
A diet that contains the correct amounts and proportions of all the necessary nutrients (carbohydrates, proteins, lipids, vitamins, minerals, water, and fibre) for health.
Malnutrition
Examiner keyword
A condition resulting from an unbalanced diet — either over-nutrition (excess intake, e.g. obesity) or under-nutrition (insufficient intake, e.g. kwashiorkor, marasmus).
Vitamin C (ascorbic acid)
Examiner keyword
A water-soluble vitamin required for collagen synthesis. Deficiency causes scurvy (bleeding gums, poor wound healing).
Dietary fibre
Examiner keyword
Indigestible plant material (mainly cellulose) that adds bulk to food in the gut, stimulates peristalsis and helps prevent constipation.
Obesity
Examiner keyword
A condition in which excess body fat has accumulated to a level that may impair health; caused by energy intake consistently exceeding energy expenditure.
Anaemia
Examiner keyword
A condition in which blood has a reduced oxygen-carrying capacity, often due to iron deficiency causing insufficient haemoglobin production.

Common Mistakes and Misconceptions — Diet

The traps other students keep falling into on diet questions — taken from recent Cambridge IGCSE 0654 examiner reports and mark schemes — and how to avoid them.

✕Stating that proteins are used only for energy
Why it happens
Students associate food with energy and apply this to all macronutrients.
How to avoid it
Proteins are primarily used for growth and repair of cells. They are an energy source only when other sources are depleted.
✕Saying vitamins provide energy
Why it happens
Students lump vitamins in with energy-providing nutrients.
How to avoid it
Vitamins do NOT provide energy. They are needed in small amounts for specific metabolic functions (e.g. vitamin C for collagen synthesis, vitamin D for calcium absorption).
✕Stating all fats are unhealthy and should be avoided
Why it happens
Media messages about diet oversimplify the role of lipids.
How to avoid it
Lipids are essential for energy storage, cell membrane structure, hormone production, and fat-soluble vitamins (A, D, E, K). Only excessive saturated fats are linked to health risks.
✕Classifying dietary fibre as a nutrient that is digested and absorbed
Why it happens
Students list fibre alongside carbohydrates and assume it is digested.
How to avoid it
Dietary fibre (cellulose) cannot be digested by humans — we lack cellulase. Its role is to add bulk and stimulate peristalsis.

Practice questions

Exam-style questions with step-by-step worked solutions. Try one before checking the method.

Past paper style quiz

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Diet — frequently asked questions

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Diet

Short Study Notes in the form of Slides

Short Study Notes — Diet

Detailed Notes

What you’ll learn

How it’s examined

1State the role of iron in the body

2Why a pregnant woman needs more protein

3Health risk of a diet high in saturated fat

4Symptoms and cause of scurvy

5Why an athlete needs more carbohydrate than an office worker

Balanced diet

Malnutrition

Vitamin C (ascorbic acid)

Dietary fibre

Obesity

Anaemia

✕Stating that proteins are used only for energy

✕Saying vitamins provide energy

✕Stating all fats are unhealthy and should be avoided

✕Classifying dietary fibre as a nutrient that is digested and absorbed

Practice questions

Past paper style quiz

Assess your understanding

Diet — frequently asked questions