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CardioPulmRenal Final > Erythrocyte Biochemistray (Pt. 2) > Flashcards

Erythrocyte Biochemistray (Pt. 2) Flashcards

1
Q

What is the general structure of heme?

A
  • heterocyclic porphyrin ring

- iron in the center

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2
Q

In heme, what state is the iron?

A

ferrous (Fe2+)

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3
Q

Where in the body is heme synthesized?

A

liver

erythroid cells of bone marrow

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4
Q

In what part of the cell does Phase I of heme synthesis occur?

A

mitochondria

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5
Q

What reaction constitutes Phase I of heme synthesis?

A

glycine + succinyl CoA
(via ALA synthase req. B6) =
aminolevulinic acid

*rate-limiting step

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6
Q

What is the rate-limiting step of heme synthesis?

A

ALA synthase

synthesis of aminolevulinic acid

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7
Q

What vitamin cofactor is needed by ALA synthase?

A

B6

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8
Q

In what part of the cell does Phase II of heme synthesis occur?

A

cytosol

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9
Q

What is the first step in Phase II of heme synthesis?

A

ALA + ALA
(via ALA dyhydratase) =
porphobilinogen (PBG)

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10
Q

What three enzymes are utilized in Phase II of heme synthesis?

A

porphobilinogen deaminase
uroporphyrinogen III synthase
uroporphyrinogen decarboxylase

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11
Q

What is the final product of Phase II in heme synthesis?

A

coproporphyrinogen III

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12
Q

Where in the cell does Phase III of heme synthesis occur?

A

mitochondria

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13
Q

What enzyme in Stage III of heme synthesis, if deficient, is responsible for variegate porphyria?

A

protoporphyrinogen IX oxidase

changes protoporphyrinogen to protoporphyrin IX

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14
Q

What enzyme changes protoporphyrin IX to heme?

A

ferrochelatase

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15
Q

What two enzymes in heme synthesis are inhibited by lead?

A

aminolevulinic acid dehydratase

ferrochelatase

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16
Q

What important biological substance, other than hemoglobin, contains heme?

A

cytochromes

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17
Q

In lead poisoning, which intermediate of heme synthesis accumulates and becomes neurotoxic?

A

aminolevulinic acid

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18
Q

What are the types of symptoms exhibited by acute hepatic porphyrias?

A

neurologic symptoms

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19
Q

What are the types of symptoms exhibited by erythropoietic porphyrias?

A

skin

photosensitivity

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20
Q

What enzyme deficiency causes acute intermittent porphyria?

A

porphobilinogen (PBG) deaminase

-in the liver

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21
Q

What are the characteristics of acute intermittent porphyria?

A
  • buildup of porphobilinogen (PBG)
  • autosomal dominant
  • periodic attacks of abdominal pain
  • periodic neuro dysfunction
  • type: hepatic
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22
Q

What enzyme deficiency causes congenital erythropoietic porphyria?

A

uroporphyrinogen III synthase

-in erythrocytes

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23
Q

What are the characteristics of congenital erythropoietic porphyria?

A

-buildup of uroporphyrinogen I and its oxidative products

  • autosomal recessive
  • red-colored teeth and urine
    type: erythropoietic
24
Q

What enzyme deficiency causes porphyria cutanea tarda?

A

uroporphyrinogen III decarboxylase

25
Q

What are the characteristics of porphyria cutanea tarda?

A
  • buildup of uroporphyrinogen III and uroporphyrinogen I
  • autosomal dominant (most common porphyria in U.S.)
  • photosensitivity, wine-colored urine
  • type: hepatoerythropoietic
26
Q

What enzyme deficiency causes variegate porphyria?

A

protoporphyrinogen IX oxidase

27
Q

What are the characteristics of variegate porphyria?

A

buildup of porphyrinogen IX

  • autosomal dominant
  • photosensitivity
  • neurologic symptoms
  • developmental delay in children
28
Q

What system degrades hemoglobin?

A

reticulo-endothelial system

29
Q

Delineate the intermediates and enzymes from heme to bilirubin.

A 
Heme
-heme oxygenase
Biliverdin
-biliverdin reductase
Bilirubin
30
Q

What enzyme removes heme from its cyclic form into a linear form?

A

heme oxygenase

the 1st rxn in heme degradation

31
Q

What are the characteristics of the first reaction in heme degradation, catalyzed by heme oxygenase?

A
  • requires oxygen
  • releases carbon monoxide
  • iron is oxidized from ferrous to ferric form
32
Q

What is needed by biliverdin reductase?

A

NADPH

33
Q

Once bilirubin is created from the degradation of heme, what happens to it?

A
  • released into the bloodstream
  • bound to albumin
  • transported to the liver
34
Q

What enzyme is needed to conjugate bilirubin in the liver?

A

UDP-glucuronyl transferase

35
Q

What other molecule is bilirubin conjugated with in the liver?

A

glucuronic acid

36
Q

What is the rate-limiting step of heme degradation?

A

conjugation of bilirubin and glucuronic acid

via UDP-glucuronyl transferase

37
Q

After conjugation, where does the bilirubin-diglucuronide go?

A
  • released into the gall bladder as bile

- secreted into small intestine in response to food

38
Q

What happens to bilirubin-diglucuronide in the intestines?

A
  • microbial reduction to urobilinogen

- further microbial reduction to stercobilin

39
Q

What happens to the portion of the urobilinogen that gets reabsorbed from the intestines?

A

it gets processed by the kidneys

-becomes urobilin

40
Q

What are normal levels of unconjugated and conjugated bilirubin in the body?

A
  1. 2-0.9 mg/dL (unconjugated)

0. 1-0.3 mg/dL (conjugated)

41
Q

What are some characteristics of pre-hepatic jaundice?

A
  • increased production of unconjugated bilirubin
  • excess hemolysis
  • capacity of liver to uptake BR is exceeded
  • Ex: internal hemorrhage, mom-baby blood group
42
Q

What would be the lab findings of a pt with pre-hepatic jaundice?

A
  • increased blood levels of unconjugated bilirubin
  • normal blood levels of conjugated bilirubin
  • normal liver enzymes
  • urobilinogen present in the urine
43
Q

What are some characteristics of intra-hepatic jaundice?

A

-impaired hepatic uptake of unconjugated bilirubin, conjugation, or secretion of conjugated bilirubin

  • generalized hepatic dysfunction
    ex: cirrhosis, Criggler-Najjar or Gilbert Syndromes
44
Q

What would be the lab findings of a pt with intra-hepatic jaundice?

A

-varying increases in unconjugated and conjugated bilirubin (depending on the cause)

  • increase in other liver markers and enzymes
  • normal urobilinogen levels in urine
45
Q

What are some characteristics of post-hepatic jaundice (aka Cholestatic Jaundice or Cholestasis)?

A
  • decreased bile flow
  • problems with bilirubin secretion
  • ex: obstruction, gall stones, tumors, drugs
46
Q

What would be the lab findings of a pt with intra-hepatic jaundice?

A

-elevated blood levels of conjugated bilirubin
-small increases in unconjugated bilirubin
(d/t bilirubin backing up)
-normal liver enzymes
-elevated alkaline phosphatase

47
Q

Why would a pt with post-hepatic jaundice have dark-colored urine?

A
  • conjugated bilirubin is present in the urine
  • no urobilinogen in the urine

-conjugated BR couldn’t get into the gut, so the liver released it back out into the bloodstream

48
Q

Why would a pt with post-hepatic jaundice have light-colored and pale stool?

A
  • no stercobilin in the feces

- conjugated BR couldn’t get into the gut, so the liver released it back out into the bloodstream

49
Q

What are some characteristics of Neonatal Jaundice?

A
  • physiological jaundice
  • immature hepatic metabolic pathways
  • -deficiency of UDP-glucuronyl transferase
  • breakdown of fetal Hb as it’s replaced by adult Hb
50
Q

How does phototherapy aid in treating jaundice?

A

-blue fluorescent light causes bilirubin to change into more soluble isomers

51
Q

Besides phototherapy, what is another treatment for jaundice and what is its mechanism of action?

A
  • intramuscular injection of tin-mesoporphyrin

- inhibition of heme oxygenase

52
Q

What is Criggler-Najjar Syndrome?

A
  • absence of or 90 percent diminshed activity of UDP-glucuronyl transferase
  • severe hyperbilirubinemia; BR accumulates in baby’s brain … encephalopathy and brain damage
53
Q

What are possible treatments for Criggler-Najjar Syndrome?

A
  • blood transfusions and phototherapy
  • hemo oxygenase inhibitors
  • oral calcium phosphate and carbonate (forms complexes with BR in the GI tract)
  • liver transplant before brain damage occurs
54
Q

What is Gilbert Syndrome?

A
  • benign disorder (2-10% of the population)
  • reduced UDP-glucuronyl transferase activity (25 percent)

-bilirubin may increase with fasting, stress, or alcohol consumption

55
Q

What is hepatitis?

A
  • inflammation of the liver, leading to liver dysfunction
  • bilirubin accumulates in skin and sclera of the eyes
  • causes: viral infection (A, B, C), alcoholic cirrhosis, liver cancer
56
Q

What are the lab findings of a patient with hepatitis?

A

elevated levels of unconjugated and conjugated bilirubin

-dark, tea-colored urine

CardioPulmRenal Final (13 decks)

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