010915 heme catab, bile salts

Question 1

where is heme catabolized

Answer 1

macrophage

Question 2

how is heme broken down?

Answer 2

heme ring opens

heme is converted to biliverdin and then bilirubin

Question 3

liver’s role in heme breakdown

Answer 3

it takes bilirubin from the blood and conjugates it with glucuronic acid so that it can be excreted in bile

Question 4

how is urobilinogen made?

Answer 4

by bacteria in the GI tract that remove glucuronic acid from conjugated bilirubin and convert it to urobilinogen

Question 5

how is urobilin made?

Answer 5

kidney converts urobilinogen to urobilin, which is excreted in urine

Question 6

first step of heme degradation uses what enzyme

Answer 6

heme oxygenase

Question 7

conversion of biliverdin to bilirubin is catalyzed by

Answer 7

biliverdin reductase

Question 8

once inside the hepatocyte, what happens to bilirubin?

Answer 8

bound to ligandin

undergoes conjugation

Question 9

conjugation of bilirubin is catalyzed by

Answer 9

UGT1A1 (uridine diphosphate glucuronosytransferase)

Question 10

action of UGT1A1

Answer 10

either one or two glucuronic acid moieties are transferred to bilirubin yielding BMG or BDG

Question 11

purpose of conjugation of bilirubin

Answer 11

so it’s more water soluble and can be secreted into bile

Question 12

hyperbilirubinemia can be divided into two classes-what are they?

Answer 12

disorders of unconjugated and conjugated type

Question 13

neonatal jaundice is due to a combo of what 3 factors?

Answer 13

LOW ACTIVITY OF UGT1A1
decreased excretory capacity of hepatocytes
increased bilirubin production secondary to accelerated destruction of fetal erythrocytes

in most cases, neonatal jaundice is innocuous however

Question 14

kernicterus appears in

Answer 14

neonatal jaundice due to high levels of UNCONJUGATED bilirubin in the brain

Question 15

tx for neonatal jaundice

Answer 15

phototherapy (changes unconjugated bilirubin to a form that can be excreted in bile)

Question 16

inherited unconjugated hyperbilirubinemia

Answer 16

Crigler-Najjar type I, type II
Gilbert Syndrome

(Crigler Najjar type I is most severe by no UDP glucuronsyltransferase activity)

Question 17

conjugated hyperbilirubinemia–genetic causes?

Answer 17

Dubin Johnson

Rotor Syndrome

Question 18

hemolytic cause of jaundice results in excess what?

Answer 18

unconjugated bilirubin

Question 19

bile acids are made from

Answer 19

cholesterol

Question 20

where are bile acids made

Answer 20

liver

Question 21

a major mechanism through which cholesterol is excreted

Answer 21

bile acids

Question 22

how are bile salts formed

Answer 22

primary and secondary bile acids are reabsorbed by the lower ileum into portal blood and taken up by hepatocytes to be conjugated to glycine or taurine, forming bile salts

Question 23

familial hypercholesterolemia-defect is in?

Answer 23

gene encoding LDL receptor

Question 24

tx of FH heterozygotes

Answer 24

bile acid binding resins
HMG Coa reductase inhibitors (statins)
diet low in cholesterol and fats