Knowledge Organiser
Part of Water Regulation · GCSE GCSE Biology revision
This topic summary covers Knowledge Organiser within Water Regulation for GCSE Biology. Topic 7: Water Regulation It is section 10 of 11 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 10 of 11
Practice
15 questions
Recall
20 flashcards
Knowledge Organiser
Key Terms
- ADH: Antidiuretic hormone; increases water reabsorption in kidney
- Osmoregulation: Control of water and salt balance in blood
- Nephron: Functional unit of the kidney
- Filtration: Forced removal of small molecules from blood into nephron
- Selective reabsorption: Return of useful substances (glucose, water) to blood
- Urea: Waste from amino acid breakdown; excreted in urine
- Collecting duct: Region where ADH controls water reabsorption
- Aquaporin: Protein channel in collecting duct wall; ADH inserts more aquaporins to increase water permeability
Must-Know Facts
- ADH is produced by hypothalamus; released by pituitary gland
- Dehydration → more ADH → more water reabsorbed → concentrated urine
- Over-hydration → less ADH → less water reabsorbed → dilute urine
- Nephron stages: Filtration → Selective Reabsorption → Excretion
- Glucose is always fully reabsorbed (glucose in urine = diabetes)
- Urea is formed in the liver; excreted by kidneys
- Dialysis (ongoing) vs transplant (long-term but limited donors)
Common Mistakes
- Saying kidneys produce ADH: ADH is produced in the hypothalamus and released by the pituitary gland — the kidneys are the target organ, not the source.
- Confusing the direction of ADH's effect: More ADH = more water reabsorbed = more concentrated (darker, lower volume) urine. Students often reverse this relationship.
- Saying glucose is excreted in urine normally: All glucose is selectively reabsorbed in healthy kidneys — glucose in urine is a sign of diabetes, not normal function.
- Omitting osmosis when explaining water reabsorption: Water moves back into the blood by osmosis down a concentration gradient — always use the word "osmosis" for the mark.
- Vague dialysis vs transplant comparisons: Give specific named advantages and disadvantages — e.g. dialysis requires several sessions per week (lifestyle impact); transplant risks rejection and requires immunosuppressants (medical risk).
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Practice Questions for Water Regulation
Where does the filtration of blood take place in the kidney?
Describe the process of selective reabsorption in the kidney and explain why it is important.
Quick Recall Flashcards
15 questions on Water Regulation — practise free
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