Hemoglobin Breakdown Products are Excreted

Question

Hemoglobin breakdown products are excreted
A) As bilirubin glucuronide in the bile
B) As urobilinogen in the urine
C) As stercobilin in the feces
D) In 4X the molar ratio to hemoglobin because hemoglobin has 4 hemes
E) All of the above are true

Accepted Answer

All of the options correctly describe the breakdown and excretion pathways of hemoglobin. Hemoglobin is broken down into bilirubin, which is then converted into bilirubin glucuronide and excreted in the bile (A). Some of this bilirubin is converted into urobilinogen by gut bacteria, which can then be excreted in the urine (B) or further converted into stercobilin and excreted in the feces (C). The molar ratio mentioned in (D) reflects the fact that each hemoglobin molecule contains four heme groups, each of which can be broken down into bilirubin, thus explaining the 4X molar ratio.