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Questions and Answers
Which organ is the primary site of bilirubin metabolism and excretion?
Which organ is the primary site of bilirubin metabolism and excretion?
What is the major conjugating group in the glucuronidation of bilirubin?
What is the major conjugating group in the glucuronidation of bilirubin?
Which enzyme catalyzes the glucuronidation of bilirubin?
Which enzyme catalyzes the glucuronidation of bilirubin?
What is the fate of conjugated bilirubin in the bile?
What is the fate of conjugated bilirubin in the bile?
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What is the color of urobilinogen?
What is the color of urobilinogen?
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What is the color of stercobilin?
What is the color of stercobilin?
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What is the main clinical laboratory test used to measure serum bilirubin?
What is the main clinical laboratory test used to measure serum bilirubin?
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Which type of bilirubin does the Van den Bergh assay measure?
Which type of bilirubin does the Van den Bergh assay measure?
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Which type of bilirubin is water-soluble (conjugated) and reacts rapidly in the Van den Bergh assay?
Which type of bilirubin is water-soluble (conjugated) and reacts rapidly in the Van den Bergh assay?
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Which of the following organs is NOT involved in the removal of senescent erythrocytes from circulation?
Which of the following organs is NOT involved in the removal of senescent erythrocytes from circulation?
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Which organ is primarily responsible for the conversion of heme to bilirubin?
Which organ is primarily responsible for the conversion of heme to bilirubin?
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What molecule is used in the catabolism of heme to yield bilirubin?
What molecule is used in the catabolism of heme to yield bilirubin?
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How is bilirubin normally processed by the liver?
How is bilirubin normally processed by the liver?
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What is the role of UDP-glucuronyl-transferase in heme catabolism?
What is the role of UDP-glucuronyl-transferase in heme catabolism?
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How is conjugated bilirubin converted back into unconjugated bilirubin?
How is conjugated bilirubin converted back into unconjugated bilirubin?
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What is the difference between direct and indirect measurements of bilirubin?
What is the difference between direct and indirect measurements of bilirubin?
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What is the biochemical basis for problems associated with neonatal jaundice?
What is the biochemical basis for problems associated with neonatal jaundice?
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What are the genetically inherited disorders of hyperbilirubiemia mentioned in the text?
What are the genetically inherited disorders of hyperbilirubiemia mentioned in the text?
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What effects do genetically inherited disorders of hyperbilirubiemia have on bilirubin lab values?
What effects do genetically inherited disorders of hyperbilirubiemia have on bilirubin lab values?
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What is the average source of bilirubin?
What is the average source of bilirubin?
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Which of the following is a characteristic of unconjugated (indirect) hyperbilirubinemia?
Which of the following is a characteristic of unconjugated (indirect) hyperbilirubinemia?
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What is the most common treatment for neonatal jaundice?
What is the most common treatment for neonatal jaundice?
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Which of the following is NOT a characteristic of Gilbert Syndrome?
Which of the following is NOT a characteristic of Gilbert Syndrome?
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Which disorder is characterized by an inherited deficiency of the MRP2 transporter?
Which disorder is characterized by an inherited deficiency of the MRP2 transporter?
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Which of the following is a characteristic of Dubin-Johnson Syndrome?
Which of the following is a characteristic of Dubin-Johnson Syndrome?
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What is the underlying mechanism of non-bile acid organic anions in the liver?
What is the underlying mechanism of non-bile acid organic anions in the liver?
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Which of the following is a characteristic of obstructive jaundice?
Which of the following is a characteristic of obstructive jaundice?
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What is the genetic basis of Gilbert-Meulengracht syndrome?
What is the genetic basis of Gilbert-Meulengracht syndrome?
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What is the prognosis of Dubin-Johnson Syndrome?
What is the prognosis of Dubin-Johnson Syndrome?
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What is the characteristic feature of hepatocellular jaundice?
What is the characteristic feature of hepatocellular jaundice?
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Study Notes
Bilirubin Metabolism and Excretion
- The liver is the primary site of bilirubin metabolism and excretion.
- Glucuronic acid is the major conjugating group in the glucuronidation of bilirubin.
- The enzyme UDP-glucuronyl-transferase catalyzes the glucuronidation of bilirubin.
- Conjugated bilirubin is excreted into the bile.
Fate of Bilirubin in the Body
- Urobilinogen is yellow.
- Stercobilin is brown.
- The main clinical laboratory test used to measure serum bilirubin is the Van den Bergh assay.
- The Van den Bergh assay measures direct bilirubin.
- Direct bilirubin is water-soluble (conjugated) and reacts rapidly in the Van den Bergh assay.
Organ Involvement in Bilirubin Removal
- The spleen is primarily responsible for the removal of senescent erythrocytes from circulation.
- The liver is primarily responsible for the conversion of heme to bilirubin.
Heme Catabolism
- The molecule biliverdin is used in the catabolism of heme to yield bilirubin.
- Bilirubin is normally processed by the liver through glucuronidation.
Enzyme Role in Heme Catabolism
- UDP-glucuronyl-transferase is involved in the conjugation of bilirubin.
Conjugation and Deconjugation
- Conjugated bilirubin is converted back into unconjugated bilirubin through deconjugation.
Bilirubin Measurement
- Direct bilirubin is measured directly using the Van den Bergh assay.
- Indirect bilirubin is measured indirectly through the difference between total bilirubin and direct bilirubin.
Neonatal Jaundice
- The biochemical basis for problems associated with neonatal jaundice is the inability of the newborn to efficiently conjugate bilirubin.
Genetic Disorders of Hyperbilirubinemia
- The genetically inherited disorders of hyperbilirubiemia mentioned are Crigler-Najjar syndrome and Gilbert-Meulengracht syndrome.
- These disorders affect bilirubin lab values, leading to elevated levels of bilirubin in the blood.
Characteristics of Unconjugated Hyperbilirubinemia
- Unconjugated (indirect) hyperbilirubinemia is characterized by elevated levels of indirect bilirubin in the blood.
Treatment of Neonatal Jaundice
- The most common treatment for neonatal jaundice is phototherapy.
Characteristics of Gilbert Syndrome
- Gilbert syndrome is NOT characterized by an inherited deficiency of the MRP2 transporter.
- It is characterized by a mild, chronic unconjugated hyperbilirubinemia.
Characteristics of Dubin-Johnson Syndrome
- Dubin-Johnson syndrome is characterized by an inherited deficiency of the MRP2 transporter.
- It is characterized by a conjugated hyperbilirubinemia.
Characteristics of Obstructive Jaundice
- Obstructive jaundice is characterized by a conjugated hyperbilirubinemia.
Hepatocellular Jaundice
- The characteristic feature of hepatocellular jaundice is a mixed pattern of unconjugated and conjugated hyperbilirubinemia.
- The genetic basis of Gilbert-Meulengracht syndrome is a deficiency in the UDP-glucuronyl-transferase enzyme.
- The prognosis of Dubin-Johnson syndrome is generally good.
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Description
Test your knowledge on bilirubin metabolism and excretion with this quiz by Vanessa De La Rosa, PhD. Learn about the catabolism of heme, the conversion of heme to bilirubin, and the liver's role in processing and excreting bilirubin. Gain a deeper understanding of this potential toxin and diagnostic marker for abnormal bilirubin metabolism.
