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GCSE Biology · key term
The liquid containing water, ions and urea that remains after filtration and selective reabsorption and is excreted from the body.
Used by AQA and OCR
Specification 4.5.3.3 · Paper 2
Revise: Kidney Function and Water ControlFiltration alone cannot produce the final urine because useful small molecules are filtered alongside wastes. Selective reabsorption is therefore needed to recover useful substances.
Specification B3.3g · Paper 1 (Foundation), Paper 3 (Higher)
A liquid produced by the kidneys that contains urea, excess water and excess ions.
Revise: Function of kidneysWater is continually gained through drinks, food and metabolic reactions, and lost in urine, sweat, faeces and exhaled air. These gains and losses vary, so the body must regulate its internal water content rather than allow it to change without control. This regulation is called osmoregulation and is part of homeostasis.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A liquid containing urea and water left after the kidneys have filtered the blood and reabsorbed substances the body needs.
Revise: Kidneys and Water BalanceThe kidneys help by controlling how much water leaves the body in urine.
When interpreting kidney data, distinguish amount from concentration and identify whether the data refer to blood, newly formed filtrate or final urine.
In an ADH question, link each step: blood too concentrated → more ADH → tubules more permeable → more water reabsorbed → smaller volume of more concentrated urine.
Link each condition to all four stages: blood water level → water reabsorption → urine volume and concentration → water excreted.
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