Human Nutrition

7. Human Nutrition — Cambridge IGCSE Biology 0610 Revision Notes & Topical Questions

5 min read 9 parts Lesson 1 of 6 1 quiz

📚 Cambridge IGCSE Biology 0610 Hub / Topical Revision

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Lesson summary

7. Human Nutrition — IGCSE BIOLOGY notes: Describe a balanced diet, food tests, the stages of digestion in the alimentary canal, and the enzymes and organs involved.Balanced diet = a diet containing carbohydrates, proteins, lipids, vitamins, minerals, dietary fibre and water in t…

Activity level
Breastfeeding
Mechanical (physical) digestion
Chemical digestion
Absorption
Assimilation

Part 1 of 7Balanced diet and nutrients

Balanced diet a diet containing carbohydrates, proteins, lipids, vitamins, minerals, dietary fibre and water in the right amounts for health and energy.

Part 2 of 7Vitamins, minerals and deficiency diseases

Nutrient	Function	Deficiency
Vitamin C	Forms collagen in skin, gums and bones	Scurvy: bleeding gums, ulcers, tooth loss, pain in limbs
Vitamin D	Helps the body absorb calcium	Rickets: soft, weak, deformed bones in children
Calcium	Strong bones and teeth; blood clotting	Weak bones; osteoporosis later in life
Iron	Makes haemoglobin in red blood cells	Anaemia
Protein	Growth and repair	Kwashiorkor: swollen abdomen and slow growth

Part 3 of 7Energy needs of different people

Age

Age young people need more energy and more protein for growth, and adult energy needs fall with age.

Activity level

Activity level the more active the person, the more energy is needed because muscles respire more.

Pregnancy

Pregnancy more energy is needed, plus extra calcium and iron for the foetus's bones, teeth and blood.

Breastfeeding

Breastfeeding energy needs rise and extra calcium is needed to make milk.

Imbalance

Imbalance too little energy gives underweight and too much is stored as fat, raising the risk of obesity, type 2 diabetes and heart disease.

Part 4 of 7Food tests

Nutrient	Test	Positive result
Starch	Add iodine solution	Brown to blue-black
Reducing sugar	Heat with Benedict's solution	Blue to green, yellow or brick-red
Protein	Add biuret reagent	Blue to purple
Fat	Shake with ethanol, then pour into water	White emulsion forms

Part 5 of 7Stages and organs of the digestive system

Ingestion

Ingestion taking food into the body through the mouth.

Mechanical (physical) digestion

Mechanical (physical) digestion breaking food into smaller pieces without changing its chemistry.

Chemical digestion

Chemical digestion breaking large insoluble molecules into small soluble ones with enzymes.

Absorption

Absorption movement of small food molecules and ions through the intestine wall into the blood.

Assimilation

Assimilation uptake and use of the absorbed nutrients by body cells.

Egestion

Egestion passing out undigested, unabsorbed food as faeces.

Alimentary canal

Alimentary canal mouth, oesophagus, stomach, small intestine, large intestine (colon, rectum, anus).
- (duodenum and ileum)
Food passes directly through these organs.

Associated organs

Associated organs salivary glands, pancreas, liver and gall bladder; food does not pass through them.

Part 6 of 7Functions of the digestive organs

Organ	Function
Mouth and salivary glands	Teeth chew food; saliva lubricates it and its amylase starts starch digestion to maltose
Oesophagus	Peristalsis (wall contractions) pushes food to the stomach
Stomach	Churning continues mechanical digestion; protease begins protein digestion; hydrochloric acid gives low pH and kills pathogens
Liver and gall bladder	Liver makes bile; gall bladder stores it and releases it into the duodenum
Pancreas	Makes amylase, protease and lipase and releases them into the duodenum
Duodenum	Bile neutralises acid and enzymes complete chemical digestion
Ileum	Digested food and water are absorbed through villi
Colon	Remaining water is absorbed and faeces are formed
Rectum and anus	Faeces are stored and then egested

Part 7 of 7Digestive enzymes and their products

Food	Enzyme	Made in	Product
Starch	Amylase	Salivary glands and pancreas	Maltose, then glucose (by maltase)
Protein	Protease	Stomach and pancreas	Amino acids
Fat	Lipase	Pancreas	Fatty acids and glycerol

Key terms

Term	Meaning
Balanced diet	A diet with all nutrients in the correct proportions for health.
Digestion	Breakdown of large insoluble food molecules into small soluble ones.
Absorption	Movement of digested food molecules into the blood or lymph.
Assimilation	Use of absorbed nutrients by body cells.
Egestion	Removal of undigested food as faeces.
Peristalsis	Wave of muscle contractions that pushes food along the gut.
Enzyme	A biological catalyst made of protein.

Avoid these mistakes

Mixing up absorption and egestion — egestion removes undigested waste that was never absorbed into the blood.

Saying fibre is digested — it is not digested but gives bulk.

Confusing excretion with egestion — faeces were never part of body cells.

Giving the end product of protein digestion as glucose — it is amino acids.

Saying emulsification by bile is chemical digestion — it is physical, because no bonds are broken.

Last updated: 14 October 2026