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WAEC Biology 2017 Question 15

Question 15

Excretion

The diagram below is an illustration of the urinary tubule in a mammal. Which of the following substances is greater in concentration in the part labelled IV when compared to that of the part labelled I?

Diagram for this question
  1. A.Lipid
  2. B.Glucose
  3. C.Urea
  4. D.Uric acid
Show the answer and explanation

Answer: C (Urea)

Explanation

As the filtrate passes along the tubule, water is reabsorbed but urea is not, so urea is much more concentrated in the collecting duct (IV) than at the start of the tubule (I).