Igcse Model Questions Vol1 2020 Biology Question 6

Practice essay / theory question 6 from the 2020 Igcse Model Questions Vol1 Biology examination. This question covers Excretion .

Igcse Model Questions Vol1 2020 Biology Essay / Theory
Topic: Excretion
Question 6 IGCSE_MODEL_QUESTIONS_VOL1 • 2020 • BIOLOGY • essay

A healthy adult has a glomerular filtration rate (GFR) of 120 mL min⁻¹. In the proximal convoluted tubule, 65 % of the filtered Na⁺ and water are re‑absorbed. In the loop of Henle, a further 15 % of the filtered water is re‑absorbed, but Na⁺ re‑absorption is negligible. In the distal convoluted tubule and collecting duct, 10 % of the remaining water is re‑absorbed under the influence of antidiuretic hormone (ADH). The remaining filtrate is excreted as urine.

Question Parts

( a )
Construct a table showing the volume of filtrate (in mL) at the end of each segment: glomerulus, proximal tubule, loop of Henle, distal tubule/collecting duct, and final urine.
( b )
Explain how the presence of ADH influences the concentration of the urine produced, linking it to the water re‑absorption calculated in part (a).
( c )
If the person becomes dehydrated and ADH secretion increases such that water re‑absorption in the distal tubule rises to 25 % of the water arriving there, recalculate the final urine volume and comment on the change in urine concentration.

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About This Question

This is Igcse Model Questions Vol1 2020 Biology Question 6. It is one of the essay questions from the 2020 Igcse Model Questions Vol1 Biology examination.

The question covers Excretion .

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