Heme

Question 1

Where is the majority of heme synthesized?

Answer 1

bone marrow

Question 2

What other molecule is dependent on the heme pathway for its synthesis?

Answer 2

cytochrome

Question 3

What two products does heme synthesis begin with?

Answer 3

glycine and succinyl-CoA

Question 4

What does ALA synthase stand for?

Answer 4

aminolevulinic acid synthase

Question 5

At what step is heme synthesis exported from the mitochondria?

Answer 5

aminolevulinic acid is exported from the mitochondria

Question 6

What stage of heme synthesis re-enters the cytosol?

Answer 6

Protoporphyrinogen IX

Question 7

What is the committed step of heme synthesis?

Answer 7

ALA synthase

Question 8

What two drugs exacerbate heme synthesis disorders?

Answer 8

alcohol and barbiturates.

induction of cytochrome p450 pathways (MEOS)

Question 9

What enzyme is affected in acute intermittent porphyria?

Answer 9

PBG deaminase

Question 10

How does acute intermittent porphyria manifest itself?

Answer 10

patient will present with dark red urine

Question 11

What enzyme is affected by porphyria cutanea tarda?

Answer 11

UPG III Decarboxylase

Question 12

How does acute porphyria cutanea tarda manifest itself?

Answer 12

under UV light, urine of patient will emit a red fluorescence

Question 13

Why can porphyrias cause photosensitivity?

Answer 13

porphyrins can absorb UV and visible light and use that energy to generate reactive oxygen species

Question 14

What two enzymes of heme synthesis are affected by lead?

Answer 14

PBG synthase and ferrechelatase

Question 15

What is the half-life of RBCs?

Answer 15

120 days

Question 16

What two organs remove damaged RBCs?

Answer 16

spleen = majority

liver = some too

Question 17

Heme oxygenase produces what two by-products?

Answer 17

carbon monoxide and Fe (III)

Question 18

What reducing equivalent does bilivedin reductase consume?

Answer 18

NADPH

Question 19

How many UGT molecules are attached to bilirubin?

Answer 19

two

Question 20

Where is bilirubin produced?

Answer 20

spleen

Question 21

How does bilirubin travel from the spleen to the liver?

Answer 21

albumin

Question 22

What do gut bacteria catalyze bilirubin into?

Answer 22

urobilinogen

Question 23

What else do the bacteria do to bilirubin?

Answer 23

remove the gluronic acid molecules

Question 24

Oxidation or urobilinogen yields what product?

Answer 24

urobilin (stercobilin)

Question 25

Where doe the yellow color of urine come from?

Answer 25

urobilins reabsorbed from the gut and renally excreted

Question 26

At what concentration of bilirubin will it enter the tissues?

Answer 26

2-3 mg/dL

Question 27

When bilirubin crosses the blood brain barrier, what is this condition called? Is this conjugated or unconjugated bilirubin?

Answer 27

kernicterus unconjugated

Question 28

What color of feces or urine indicates a bilirubin conjugation deficiency?

Answer 28

pale

Question 29

What drug can interfere with bilirubin conjugation?

Answer 29

acetominophen

Question 30

How does a blocked bile duct lead to jaundice?

Answer 30

impedes liver's ability to excrete conjugated bilirubin into the feces

Question 31

What two tenets can suggest cholestatic jaundice?

Answer 31

pale feces and dark urine

Question 32

What marker is indicative of a blocked bile duct?

Answer 32

alkaline phosphatase in serum

Question 33

Synthesis of what kind of detoxification enzymes consumes heme? How does this affect heme synthesis?

Answer 33

Cytochrome p450 increases heme synthesis by removing feedback inhibition

Question 34

How does bilirubin get from the spleen to the liver?

Answer 34

albumin!

Question 35

Bacterial processing of conjugated bilirubin in the gut produces what compound?

Answer 35

urobilinogens

Question 36

What else do intestinal bacteria due to conjugated heme?

Answer 36

remove the glucoronic acid molecules

Question 37

oxidation of urobilinogen yields what?

Answer 37

urobilin (feces color)

Question 38

What gives urine its color?

Answer 38

reabsorbed urobilinogens from the gut

Question 39

What is the criteria for diagnosis of hyperbilirubinemia?

Answer 39

1.5 mg/dL | bilirubin enters tissues at 2-3 mg/dL

Question 40

What type of bilirubin can cross the blood brain barrier?

Answer 40

unconjugated bilirubin

Question 41

What drug can cause hepatic jaundice?

Answer 41

acetominophen

Question 42

What are the color of urine and feces in cholestatic jaundice?

Answer 42

dark urine and pale feces

Question 43

Congenital erythropoietic porphyria is caused by a defeciency in what enzyme?

Answer 43

UPG III Synthetase