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Question 304
Physiology → Haematology
Classification
Question
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During normal erythrocyte destruction in the reticuloendothelial system, haemoglobin is separated into iron, globin and porphyrin. What happens to the iron?
Question Stem
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Options
A
It is retained and reused
B
It is converted directly into bilirubin
C
It is excreted with globin
D
It is transported to the liver as porphyrin
E
It is lost from the body after each erythrocyte is destroyed
Explanation
Erythrocytes have a lifespan of approximately 120 days and are broken down by the reticuloendothelial system. Haemoglobin is separated into iron, globin and porphyrin, and the iron is retained for reuse.
Option Validity
B) Bilirubin is derived through haemoglobin breakdown but does not state that iron is directly converted into bilirubin. Iron is specifically retained and reused.
C) separates haemoglobin into iron, globin and porphyrin. It does not describe iron as being excreted together with globin.
D) bilirubin as being carried by plasma protein to the liver. Iron is instead retained for subsequent reuse.
E) Normal erythrocyte breakdown does not result in obligatory loss of the recovered iron. explicitly states that iron is retained and reused.
Further Reading
Saxena. Textbook for MRCOG-1. Physiology - Haematology - Red Blood Cell Breakdown, p.68.