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Biochem III > Heme > Flashcards

Heme Flashcards

1
Q

Where is the majority of heme synthesized?

A

bone marrow

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2
Q

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

A

cytochrome

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3
Q

What two products does heme synthesis begin with?

A

glycine and succinyl-CoA

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4
Q

What does ALA synthase stand for?

A

aminolevulinic acid synthase

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5
Q

At what step is heme synthesis exported from the mitochondria?

A

aminolevulinic acid is exported from the mitochondria

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6
Q

What stage of heme synthesis re-enters the cytosol?

A

Protoporphyrinogen IX

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7
Q

What is the committed step of heme synthesis?

A

ALA synthase

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8
Q

What two drugs exacerbate heme synthesis disorders?

A

alcohol and barbiturates.

induction of cytochrome p450 pathways (MEOS)

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9
Q

What enzyme is affected in acute intermittent porphyria?

A

PBG deaminase

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10
Q

How does acute intermittent porphyria manifest itself?

A

patient will present with dark red urine

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11
Q

What enzyme is affected by porphyria cutanea tarda?

A

UPG III Decarboxylase

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12
Q

How does acute porphyria cutanea tarda manifest itself?

A

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

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13
Q

Why can porphyrias cause photosensitivity?

A

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

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14
Q

What two enzymes of heme synthesis are affected by lead?

A

PBG synthase and ferrechelatase

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15
Q

What is the half-life of RBCs?

A

120 days

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16
Q

What two organs remove damaged RBCs?

A

spleen = majority

liver = some too

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17
Q

Heme oxygenase produces what two by-products?

A

carbon monoxide and Fe (III)

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18
Q

What reducing equivalent does bilivedin reductase consume?

A

NADPH

19
Q

How many UGT molecules are attached to bilirubin?

A

two

20
Q

Where is bilirubin produced?

A

spleen

21
Q

How does bilirubin travel from the spleen to the liver?

A

albumin

22
Q

What do gut bacteria catalyze bilirubin into?

A

urobilinogen

23
Q

What else do the bacteria do to bilirubin?

A

remove the gluronic acid molecules

24
Q

Oxidation or urobilinogen yields what product?

A

urobilin (stercobilin)

25
Q

Where doe the yellow color of urine come from?

A

urobilins reabsorbed from the gut and renally excreted

26
Q

At what concentration of bilirubin will it enter the tissues?

A

2-3 mg/dL

27
Q

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

A

kernicterus

unconjugated

28
Q

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

A

pale

29
Q

What drug can interfere with bilirubin conjugation?

A

acetominophen

30
Q

How does a blocked bile duct lead to jaundice?

A

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

31
Q

What two tenets can suggest cholestatic jaundice?

A

pale feces and dark urine

32
Q

What marker is indicative of a blocked bile duct?

A

alkaline phosphatase in serum

33
Q

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

A

Cytochrome p450

increases heme synthesis by removing feedback inhibition

34
Q

How does bilirubin get from the spleen to the liver?

A

albumin!

35
Q

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

A

urobilinogens

36
Q

What else do intestinal bacteria due to conjugated heme?

A

remove the glucoronic acid molecules

37
Q

oxidation of urobilinogen yields what?

A

urobilin (feces color)

38
Q

What gives urine its color?

A

reabsorbed urobilinogens from the gut

39
Q

What is the criteria for diagnosis of hyperbilirubinemia?

A

1.5 mg/dL

bilirubin enters tissues at 2-3 mg/dL

40
Q

What type of bilirubin can cross the blood brain barrier?

A

unconjugated bilirubin

41
Q

What drug can cause hepatic jaundice?

A

acetominophen

42
Q

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

A

dark urine and pale feces

43
Q

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

A

UPG III Synthetase

Biochem III (9 decks)

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