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Came across a question asking about "which of the following is a product of heme degradation?" and I never got the final answer...
A. Porphobilinogen
B. Uroporphyrinogen
C. Protoporphyrin
D. Urobilinogen
I was between answers C and D based on the following:
According to PATHOMA: Hemoglobin is broken down into Heme + Globin -> Globin is broken down into amino acids while the heme is broken down into Protoporphyrin + iron -> The Protoporphyrin is then broken down into unconjugated bilirubin -> Unconjugated bilirubin binds to albumin and transferred to the liver for conjugation -> conjugated bilirubin is then excreted into the bile (this is as far as Pathoma goes in terms of the heme degradation pathway)
According to RX: Hemoglobin is broken down into Heme + Globin -> the heme is then subsequently converted to Biliverdin (via macrophage Heme Oxygenase) -> Biliverdin is then converted to unconjugated bilirubin (via biliverdin reductase) -> unconjugated bilirubin binds to albumin and transferred to the liver for conjugation -> conjugated bilirubin is then excreted into the bile -> Conjugated bilirubin then travels from the bile into the intestines -> In the intestines, an enzyme produced by bacteria called β-glucuronidase hydrolyzes the glucuronic acid, reforming unconjugated bilirubin -> Other bacterial-mediated processes in the intestine then convert unconjugated bilirubin in to urobilinogen (the pathway then continues to describe the conversion of urobilinogen to stercobilin for excretion in feces, or into urobilin for excretion in the urine)
When I read the question, my first instinct was to look for biliverdin or Bilirubin as answer choices since they are definitely products of heme degradation (via heme oxygenase and biliverdin reductase respectively) but they weren't answer choices. Considering that answers (A) and (B) are involved in the synthesis of Heme (and not it's degradation), I was able to cancel these out. Using some MCQ testing strategies, I decided that I could also then cancel out (C) Protoporphyrin because it's also definitely involved in heme synthesis, whereas Urobilinogen is definitely not.
My dilemma stems from the following then:
1) Is Protoporphyrin an actual "product" of heme degradation like Pathoma says? Is there some small nuance between Protoporphyrin and Biliverdin? That is, is Biliverdin considered a protoporphyrin (their structures are very similar see attached figures)? (MY ORGO SUCKS lol)
2) Is Urobilinogen considered an actual "product" of heme degradation considering it happens 4-5 steps after the initial degradation of heme into biliverdin?
A. Porphobilinogen
B. Uroporphyrinogen
C. Protoporphyrin
D. Urobilinogen
I was between answers C and D based on the following:
According to PATHOMA: Hemoglobin is broken down into Heme + Globin -> Globin is broken down into amino acids while the heme is broken down into Protoporphyrin + iron -> The Protoporphyrin is then broken down into unconjugated bilirubin -> Unconjugated bilirubin binds to albumin and transferred to the liver for conjugation -> conjugated bilirubin is then excreted into the bile (this is as far as Pathoma goes in terms of the heme degradation pathway)
According to RX: Hemoglobin is broken down into Heme + Globin -> the heme is then subsequently converted to Biliverdin (via macrophage Heme Oxygenase) -> Biliverdin is then converted to unconjugated bilirubin (via biliverdin reductase) -> unconjugated bilirubin binds to albumin and transferred to the liver for conjugation -> conjugated bilirubin is then excreted into the bile -> Conjugated bilirubin then travels from the bile into the intestines -> In the intestines, an enzyme produced by bacteria called β-glucuronidase hydrolyzes the glucuronic acid, reforming unconjugated bilirubin -> Other bacterial-mediated processes in the intestine then convert unconjugated bilirubin in to urobilinogen (the pathway then continues to describe the conversion of urobilinogen to stercobilin for excretion in feces, or into urobilin for excretion in the urine)
When I read the question, my first instinct was to look for biliverdin or Bilirubin as answer choices since they are definitely products of heme degradation (via heme oxygenase and biliverdin reductase respectively) but they weren't answer choices. Considering that answers (A) and (B) are involved in the synthesis of Heme (and not it's degradation), I was able to cancel these out. Using some MCQ testing strategies, I decided that I could also then cancel out (C) Protoporphyrin because it's also definitely involved in heme synthesis, whereas Urobilinogen is definitely not.
My dilemma stems from the following then:
1) Is Protoporphyrin an actual "product" of heme degradation like Pathoma says? Is there some small nuance between Protoporphyrin and Biliverdin? That is, is Biliverdin considered a protoporphyrin (their structures are very similar see attached figures)? (MY ORGO SUCKS lol)
2) Is Urobilinogen considered an actual "product" of heme degradation considering it happens 4-5 steps after the initial degradation of heme into biliverdin?
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