Biology Homeostasis PMDC Conceptual Practice
PMDC Verified Question 4 of 99
An inherited metabolic disorder characterized by urine that rapidly turns black upon exposure to atmospheric oxygen is:
A
Phenylketonuria
B
Sickle cell anemia
C
Hemophilia
D
Alkaptonuria
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Alkaptonuria
Concept: Inborn errors of amino acid metabolism.

Solution: Alkaptonuria is caused by a deficiency in homogentisate 1,2-dioxygenase, leading to the accumulation of homogentisic acid in urine. Upon oxidation in air, homogentisic acid polymerizes into a dark, black pigment.

Why other options are incorrect:
  • Option A (Phenylketonuria): Caused by phenylalanine hydroxylase deficiency; urine does not turn black.

  • Option B & Option C (Sickle cell anemia & Hemophilia): Genetic hematological disorders affecting hemoglobin structure and blood clotting, respectively.

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