28. Bilirubin Flashcards Preview

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Flashcards in 28. Bilirubin Deck (19):
1

Heme is metabolized by heme oxygenase to ......, which is subsequently reduced to ..........
,

biliverdin....bilirubin.

2

Unconjugated bilirubin is removed from blood by

liver, conjugated with glucuronate and excreted
in bile.

3

Direct bilirubin—

conjugated with glucuronic acid; water soluble.

4

Indirect bilirubin—

unconjugated; water insoluble.

5

• A patient with hemolytic anemia would be likely to have which abnormal result on liver function tests?

Unconjugated hyperbilirubinemia (bilirubin is a breakdown product of heme)

6

• What is the essential structural difference between direct and indirect bilirubin?

Direct bilirubin is conjugated with glucuronic acid and is thus water soluble, whereas indirect bilirubin is not and is thus water insoluble

7

• How is bilirubin excreted from the body?

Bilirubin is excreted in bile (it is excreted in urine as urobilin and stool as stercobilin)

8

• What type of bilirubin is water soluble: direct or indirect? What type is water insoluble?

Direct bilirubin is water soluble; indirect bilirubin is water insoluble

9

• Unconjugated bilirubin travels through the circulation bound to ____. This complex can be measured as ____.

Albumin; indirect bilirubin

10

• A patient with impaired bile acid conjugation would develop which abnormality on liver function tests?

Conjugated (direct) hyperbilirubinemia

11

• ____ is excreted renally, giving ____ its classic yellow color.

Urobilin; urine

12

• If exposed to conjugated bilirubin, colonic bacteria will produce what?

Urobilinogen

13

• A patient taking antibiotics wipes out his gut flora. His urine is noted to be paler than usual. Why is this the case?

Bilirubin conversion into urobilinogen is impaired; reabsorbed urobilinogen is converted into urobilin, giving urine its yellow color

14

• About ____% of urobilinogen is excreted as stercobilin in feces and about ____% goes to the kidney and liver.

80; 20

15

• Of the urobilinogen that goes to the kidneys and liver, about ____% is excreted renally and ____% enters the enterohepatic circulation.

10; 90

16

• A patient with an obstruction in stercobilin deposition has feces of what characteristic color?

Pale stools (obstruction inhibits its ability to be deposited in the gastrointestinal lumen, leading to pale stools)

17

• Urobilinogen cannot be excreted in urine. What form is it excreted in feces, and in a normal patient, what color is the stool?

Excreted in feces as stercobilin, which causes the brown color of stool

18

• In an experiment, tagged urobilinogen in the gut can be expected to be later found in which organ?

Liver, via enterohepatic circulation

19

• Which enzyme catalyzes bilirubin conjugation?

UDP-glucuronosyltransferase

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