Biochemistry

Question 1

bilirubin consists of an open chain of four pyrrole rings (tetrapyrrole)

Answer 1

c

Question 2

bilirubin is a breakdown product of blood, usually produced in the spleen

Answer 2

c

Question 3

macrophages break down senescent erythrocytes and transform the haem into

Answer 3

c

Question 4

biliverdin that normally rapidly reduces to free bilirubin

Answer 4

c

Question 5

bilirubin is yellow in colour.

Answer 5

c

Question 6

some of the double-bonds in bilirubin isomerize when exposed to light and this is used in the phototherapy of jaundiced newborns. The E,E-isomer of bilirubin formed upon light exposure is more soluble than the Z,Z-isomer

Answer 6

c

Question 7

bilirubin measurement is a standard pathology laboratory test

Answer 7

c

Question 8

bilirubin is neurotoxic at high levels in the newborn (presents as kernicterus)

Answer 8

c

Question 9

hyperbilirubinemia gives rise to jaundice

Answer 9

c

Question 10

urobilinogen is a colourless product of bilirubin reduction. It is formed in the intestines by bacterial action. Some urobilinogen is reabsorbed from the gut and excreted by the kidney. This constitutes the normal “enterohepatic urobilinogen cycle”

Answer 10

c

Question 11

the chemical forms of bilirubin are unconjugated (indirect) and conjugated (direct)
bilirubin is excreted as the glucuronide (conjugated) in bile

Answer 11

c

Question 12

elevated levels of bilirubin can be caused by neonatal hyperbilirubinaemia, bile duct obstruction, Severe liver failure with cirrhosis, Crigler-Najjar syndrome, Dubin-Johnson syndrome and chronic or acute blockage of the bile duct (choledocholithiasis )

Answer 12

c