MCQs on Bilirubin Metabolism: Biochemistry

Multiple Choice Question on 

Bilirubin Metabolism and Related Disorders

1) Bilirubin is generated from the catabolism (breakdown) of protoporphyrin IX through a microsomal enzyme in a two reaction step. In the first step, the tetrapyrrole ring is opened to produce biliverdin which is subsequently converted into bilirubin through further reduction.

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)  0-100 mg
d) 250-350 mg

3) Bilirubin, generated in the spleen and bone marrow, enters the bloodstream, where it subsequently attaches to albumin for transport to the liver. Within the hepatocytes bilirubin binds to Ligandin Y protein (a GST gene family protein). 

The bilirubin is transported into the hepatocytes by which of the following process?
a) passive diffusion 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. 

Which of the following transporter protein is involved in this process?
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 called.....................................?
a) UDP-Glucuronosyl transferase
b) Biliverdin reductase
c) Heme oxygenase
d) beta-glucuronidase

9) Urobilinogen undergoes oxidation to create a pigmented substance that imparts the distinctive color to both urine and feces.

In which type of jaundice, the stool is clay-colored due to the lack of chemical 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 known as..............................................
a) Heme oxygenase
b) UDP-Glucouronyl transferase
c) beta-glucuronidase
d) MRP-2 protein

Multiple Choice Answers:
1-c) Heme deoxygenase and Biliverdin reductase
2-d) 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-a) UDP-Glucuronosyl transferase
9-c) Obstructive jaundice
10-d) MRP-2 protein