Bilirubin Metabolism: MCQ

Multiple Choice Question  on 
Bilirubin Metabolism and Related Disorders

1) Bilirubin is produced from the catabolism of protoporphyrin IX by a microsomal enzyme in a two reaction step. The first step involves the opening of the tetrapyrrole ring to form biliverdin. Biliverdin is further reduced to form bilirubin. What are the enzymes responsible for these two steps?
a) Heme dehydrogenase and Bilirubin oxygenase
b) Heme oxygenase and Biliverdin reductase
c) Heme deoxygenase and Biliverdin reductase
d) Heme oxygenase and Bilirubin reductase

2) Approximately 85% of the total bilirubin produced is derived from senescent red blood cells in the reticuloendothelial cells of the liver, spleen, and bone marrow. The remaining 15% of bilirubin is produced from RBC precursor during ineffective erythropoiesis, myoglobin, cytochromes, and peroxidases. The daily production of bilirubin is
a) 500-1000 mg
b) 100-250 mg
c) 250-350 mg
d) 0-100 mg

3) The bilirubin produced in the spleen and bone marrow diffuses into the blood, binds to albumin transported to the liver, and binds to Ligandin Y protein (a GST gene family protein) inside the hepatocytes. The bilirubin is transported into the hepatocytes via
a) passive diffusion of bilirubin into hepatocytes
b) carrier-mediated saturable system
c) active transport coupled with Na K ATPase
d) MRP2 protein

4) The unconjugated bilirubin (non-polar form) is converted into a more polar form by conjugating with glucuronic acid. The stepwise addition of two glucuronic acids to bilirubin result in bilirubin diglucuronides. The enzyme that catalyzes the formation of bilirubin diglucuronide is
a) Bilirubin UDP-glucuronides synthase
b) Bilirubin UDP-glucuronides mutase
c) Bilirubin UDP-glucuronosyltransferase
d) Bilirubin UDP-glucuronosyl isomerase

5) The secretion of bilirubin from hepatocytes to canaliculi is an energy-dependent process. The transporter protein involved in this protein is
a) MRP2 protein
b) active transport coupled with Na K ATPase
c) Bilirubin transporting protein
d) Chylomicron

6) In the intestine, bacterial degradation of bilirubin forms urobilinogen. Urobilinogen is a colorless bilirubin derived product that is further oxidized to form the following pigments except
a) Urobilin
b) Mesobilin
c) Stercobilin
d) Exobilin

7) Gilbert's syndrome is the genetic disorder of bilirubin metabolism and the defect lies in the uptake of bilirubin. Which of the following form of bilirubin is elevated in these subjects?
a) Direct bilirubin and Total bilirubin
b) Indirect and total bilirubin
c) Both direct and indirect bilirubin
d) None

8) Crigler Najjar Syndrome is the inherited metabolic disorder of bilirubin metabolism due to a defective enzyme
a) Heme oxygenase
b) Biliverdin reductase
c) UDP-Glucuronosyl transferase
d) beta-glucuronidase

9) Urobilinogen is oxidized to form a colored product and these give the characteristic color of urine and feces. In which type of jaundice, the stool color is clay-colored because of lack of urobilin?
a) Hemolytic jaundice
b) Viral hepatitis
c) Obstructive jaundice
d) Alcoholic cirrhosis

10) Dubin Johnson syndrome is the inherited metabolic disorder of bilirubin metabolism due to a defective protein
a) Heme oxygenase
b) UDP-Glucouronyl transferase
c) MRP-2 protein
d) beta-glucuronidase

Multiple Choice Answers
1-c) Heme deoxygenase and Biliverdin reductase
2-c) 250-350 mg
3-a) passive diffusion of bilirubin into hepatocytes
4-c) Bilirubin UDP-glucuronosyltransferase
5-a) MRP2 protein
6-d) Exobilin
7-b) Indirect and total bilirubin
8-c) UDP-Glucuronosyl transferase
9-c) Obstructive jaundice
10-c) MRP-2 protein

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