A man produces 180 litres of glomerular filtrate per day but excretes only 1.8 litres of urine. What percentage of the filtrate is reabsorbed by the kidney tubules?
A1%
B89%
C99%CORRECT
D98%
GCEBiologyExcretion2020
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Why the answer is C, and why the others tempt you.
The volume reabsorbed is 180 − 1.8 = 178.2 litres. The percentage reabsorbed is (178.2 ÷ 180) × 100 = 99%. This reflects the kidney's remarkable efficiency in recovering water and solutes from the filtrate, with only about 1% of the filtrate ultimately excreted as urine.
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