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Separate Biology · Paper 2 · Foundation + Higher · B5

Water balance and kidney processes

Key ideas1 of 3

Water gains and losses

Cells need a suitable water balance. If body fluids become too concentrated, cells can lose water by osmosis; if they become too dilute, cells can gain too much water. Either change can impair cell function. Water leaves the lungs during exhalation. Sweat removes water, ions and urea. These losses are not adjusted specifically to maintain the body water balance.

Functional diagram of blood, a filtered liquid and liquid leaving the kidney. Stages A and X are marked.

Next: Dialysis and kidney transplants →
Practice, downloads and sources

Daily 5 · Exam practice · Revision sheet ↓

Foundation + Higher · B5. Use alongside the shared B5 lessons.

AQA GCSE Biology 8461 · 4.5.3.3. Original notes, questions and diagrams. Models are simplified; teaching data are illustrative.