Learning focus
Build precise biological explanations, interpret diagrams and data, and connect structure, process and practical evidence.
Scurvy
Vitamin C deficiency causes scurvy. Collagen and other connective tissues are poorly maintained, so gums may bleed, wounds heal slowly and tissues weaken. Fresh fruit and vegetables, especially citrus and peppers, are useful sources. The explanation should link the vitamin deficiency to symptoms rather than merely naming the disease.
Rickets
Vitamin D deficiency reduces effective calcium absorption and use. Calcium deficiency also compromises mineralisation. In growing children, bones may become soft and deform under body weight, producing rickets. Vitamin D can be obtained from some foods and is also formed in skin exposed to suitable sunlight.
Anaemia
Iron is required for haemoglobin. If intake or absorption is insufficient, the blood transports less oxygen. Cells receive less oxygen for aerobic respiration, so tiredness, weakness and shortness of breath may occur. Anaemia has several possible causes, but the syllabus focuses on iron deficiency.
Malnutrition and obesity
Malnutrition means poor nutrition and includes inadequate intake, excess intake and imbalance. Protein-energy malnutrition impairs growth and tissue repair. Obesity results when energy intake repeatedly exceeds expenditure, increasing the risk of several diseases. Body mass alone does not reveal every nutrient deficiency.
Public-health reasoning
Improving nutrition may require education, food fortification, affordable varied foods, disease control and clean water. Simply advising people to eat differently may ignore cost and access. Evaluation questions reward balanced discussion of biological and social factors.
Practical or data skill
Interpret a set of fictional patient symptoms and dietary histories. Match each case to a likely deficiency and explain the biological link. State that real diagnosis requires qualified medical assessment.
Examination tip
Do not interchange rickets and scurvy. Rickets is linked to vitamin D or calcium deficiency; scurvy is linked to vitamin C deficiency.
Review questions and suggested answers
Question 1
Why does iron deficiency cause tiredness?
Suggested answer
Less haemoglobin is made, so less oxygen reaches cells for aerobic respiration.
Question 2
Name one symptom of scurvy.
Suggested answer
Bleeding gums or poor wound healing.
Question 3
How can both undernutrition and obesity be forms of malnutrition?
Suggested answer
Both result from an unsuitable nutrient or energy intake, even though one involves too little and the other often involves excess.
