Metabolism of Bilirubin

Question 1

Is unconjugated bilirubin (UCB) water soluble?

Answer 1

No- it is lipid soluble

Question 2

haemoglobin breaks down into?

Answer 2

1. heme
2. globin
   1a. bilirubin (UCB)
   1b. Fe+

Question 3

which enzyme breaks haemoglobin down?

Answer 3

heme oxygenase bilirubin reductase

Question 4

what happens to excess globin?

Answer 4

recycled for erythropoiesis.

Question 5

what can bind to UCB before entering the liver system

Answer 5

1. Albumin, most common
2. High density lipoproteins
   infrequently circulates in blood as UCB

Question 6

what other than Hb forms bilirubin?

Answer 6

Myoglobin and cytochrome enzymes

Question 7

UCB enters the liver system- what happens next?

Answer 7

albumin dissociates from the UCB, UCB is taken up by hepatocytes while albumin remains in blood.

Question 8

by which method is UCB taken into hepatocytes

Answer 8

facilitated diffusion- from area of high to low using a channel protein.

Question 9

which process does UCB go through in the liver?

Answer 9

glucuronidation

Question 10

how does glucuronidation change UCB

Answer 10

makes it more water soluble- allows for excretion in urine and feces. forms Conjugated Bilirubin

Question 11

which enzymes cause glucuronidation?

Answer 11

Uridine 5’-diphospho-glucuronosyltransferase
B- UGT

Question 12

what percent of bilirubin in small intestine is conjugated?

Answer 12

98%

Question 13

what is the large intestines effect on the conjugated bilirubin?

Answer 13

bacteria oxidises CB, forming urobilinigens

Question 14

some urobilinogen’s re-enter the enterohepatic system- what do they colour?

Answer 14

urine

Question 15

hat do the majoroity of urobilinogens colour?

Answer 15

feces eg stercobilinogens

Question 16

which type of bilirubin causes jaundice

Answer 16

both UCB and CB

Question 17

which disorders are associated with UCB jaundice?

Answer 17

non liver dysfunction disorders.
-dyserythropoesis
-extravascular haemolysis
-intravascular haemolysis
-extravasation
-medications
-gilberts syndrome

Question 18

which disorders are asscoated with CB jaundice

Answer 18

intra hepatic
-hepatitis (all)
-drugs eg steroids
-sepsis
- TPN
Post hepatic
- cholelithiasis (gall bladder stones)
- gall bladder cancer
-pancreatic cancer

Question 19

initial investigations into jaundice

Answer 19

liver function tests
-AST, ALT- if increased shows liver tissue damage
-GGT, ALP- biliary injury or intrahepatic issues.

Question 20

if results of LFT are not deranged what does this show

Answer 20

jaundice is caused by UCB, use haemolysis

Question 21

if results of LFT are deranged what does this show

Answer 21

jaundice is caused by CB