Igcse Model Questions Vol1 2017 Biology Question 6

Practice essay / theory question 6 from the 2017 Igcse Model Questions Vol1 Biology examination. This question covers Excretion .

Igcse Model Questions Vol1 2017 Biology Essay / Theory
Topic: Excretion
Question 6 IGCSE_MODEL_QUESTIONS_VOL1 • 2017 • BIOLOGY • essay

A laboratory investigation measures the concentrations of urea and creatinine in the urine of a patient. Over a 24‑hour period the urine volume collected is 1.8 L. The concentrations are: urea = 15 g L⁻¹, creatinine = 0.9 g L⁻¹. The plasma creatinine concentration is 0.09 g L⁻¹.

Question Parts

( a )
Calculate the total amount (in grams) of urea and of creatinine excreted in the 24‑hour urine sample.
( b )
Using creatinine clearance as an estimate of glomerular filtration rate, calculate the creatinine clearance in millilitres per minute. Use the formula Clearance = (U × V) / P, where U is the urine concentration (g L⁻¹), V is the urine flow rate (L min⁻¹) and P is the plasma concentration (g L⁻¹).
( c )
Discuss two physiological mechanisms by which the kidney conserves water while still eliminating waste products.
( d )
If a patient with impaired renal function shows a plasma urea concentration of 0.5 g L⁻¹ while the urine volume falls to 0.9 L per day (urine urea concentration remains 15 g L⁻¹), explain why the plasma urea level rises despite the unchanged urine concentration.

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About This Question

This is Igcse Model Questions Vol1 2017 Biology Question 6. It is one of the essay questions from the 2017 Igcse Model Questions Vol1 Biology examination.

The question covers Excretion .

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