Exam Focus

Exam Focus

Water regulation is tested in almost every AQA Paper 2 sitting. The most common question types are:

Edexcel (1BI0/2): Water regulation (osmoregulation) is examined on Edexcel Paper 2 (1BI0/2) within Topic 7. Edexcel frequently sets scenario-based questions — for example, a person who has drunk a large volume of water or exercised heavily — and asks students to predict urine concentration and explain using ADH. Graph interpretation questions showing ADH levels vs urine output are common. The key phrase for Edexcel mark schemes is "ADH increases the permeability of the collecting duct, so more water is reabsorbed by osmosis."

• 6-mark extended response: "Explain how ADH controls water levels in the blood" — cover the stimulus (dehydration), osmoreceptors, pituitary release, effect on collecting duct, reabsorption, and negative feedback for full marks.
• Graph interpretation: ADH concentration vs urine volume graphs — as ADH rises, urine volume falls. Describe the relationship using data from the graph.
• Compare dialysis and transplant (4 marks): Always give balanced points — advantage and disadvantage of each, not just lists about one treatment.
• Urine concentration questions: State whether a given scenario (exercise, drinking alcohol, diabetes insipidus) produces concentrated or dilute urine and explain why using ADH.

Key phrase to use: "ADH increases the permeability of the collecting duct, so more water is reabsorbed into the blood by osmosis."