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hematology > Unit 4 - Hgb Synthesis > Flashcards

Unit 4 - Hgb Synthesis Flashcards

1
Q

What is 90% of the dry weight of RBCs?

A

Hemoglobin

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2
Q

What is most of internal RBC metabolism geared toward?

A

Maintaining Hgb function

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3
Q

What promotes gas exchange in the capillaries in RBCs?

A

RBC membrane structure and deformability

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4
Q

What kind of protein is hemoglobin?

A

Conjugated protein

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5
Q

What is the molecular weight of hemoglobin

A

~67,000

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6
Q

How much of the RBC does hemoglobin occupy?

A

1/3 the mass of the RBC

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7
Q

Moieties means

A

portions

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8
Q

What is heme made up of?

A

Iron + porphyrin ring

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9
Q

How many heme per RBC?

A

4 per molecule

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10
Q

What is globin made up of?

A

Protein portion

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11
Q

How many chains of globin in an RBC?

A

4 chains
2 chains of one type
2 chains of another type (a2B2)

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12
Q

How much hgb synthesis at pronormoblast stage?

A

Minimal

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13
Q

How much hgb synthesis at normoblast stage?

A

Maximum

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14
Q

What stage of RBC is producing the least amount of hgb synthesis?

A

Pronormoblast

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15
Q

What stage of RBC is producing the most amount of hgb synthesis?

A

Normoblast

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16
Q

What happens to mRNA production after nucleus is extruded?

A

No new mRNA is produced

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17
Q

What does the remaining mRNA in a reticulocyte do?

A

Continues hgb synthesis

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18
Q

Hgb from retic synthesis is ___ of total hgb in rbc

A

20-25%

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19
Q

Biochemical pathways for synthesis include

A

Heme portion
Global portion
Assembly of molecule

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20
Q

Different forms of hemoglobin

A

Normal human hgb types
Variant human hgb due to genetics
Chemically modified hemoglobin variants

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21
Q

Heme is also known as

A

Ferroprotoporphyrin

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22
Q

What is the heme structure

A

Ring structure of 4 pyrrole rings attached together at methylene bridges

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23
Q

What is the ring structure of heme called

A

Protoporphyrin

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24
Q

What are the 4 rings that join in a heme?

A

Pyrrole

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25
Q

What is it that holds the 4 pyrrole rings together in a heme group?

A

Methylene bridges

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26
Q

What is at the center of the protoporphyrn?

A

Ferrous iron

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27
Q

What form of iron cannot bind oxygen?

A

Ferric iron

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28
Q

What is heme considered in biochemical terms

A

A prosthetic group attached to a protein

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29
Q

What are globin chains

A

Protein chains folded into complex tertiary structure with a pocket to hold heme

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30
Q

Normal globin
variants are named by what?

A

Greek letters

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31
Q

What kind of structure is hemoglobin?

A

A tetramer of protein chains, 2 of each type

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32
Q

What are the heme moiety

A

Iron
Glycine
Succinyl Co-A

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33
Q

What are the global moiety

A

Amino acids

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34
Q

When does hemoglobin synthesis occur

A

Pronormoblast stage through reticulocyte stage

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35
Q

Where in the cell is heme produced

A

Mitochondria
Cytoplasm

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36
Q

Where in the cell is globin produced

A

Ribosomes

37
Q

What is the rate limiting step and regulatory point of heme synthesis?

A

Glycine + succinyl CoA -> Delta ALA

38
Q

What is the first step of heme synthesis?

A

Glycine + succinyl CoA –> Delta ALA

39
Q

What is the second step of Heme synthesis?

A

Delta ALA moves into cytoplasm

40
Q

What is the third step of Heme synthesis?

A

2 Delta ALA condense into pyrrole, porphobilinogen (PBG)

41
Q

4 PBG form what kind of structure?

A

Linear structure

42
Q

What are the two rings formed after porphobilinogen forms?

A

Uroporphyrinogen
Coproporphyrinogen

43
Q

What happens after the formation of coproporphyrinogen in the cytoplasm?

A

Coproporphyrinogen returns to the mitochondria

44
Q

What occurs once coproporphyrinogen returns to the mitochondria?

A

COP undergoes two oxidation steps
COP III –> Protoporphyrinogen IX
PRO IX –> Protoporphyrin IX

45
Q

What is the final step of heme synthesis in the mitochondria?

A

Protoporphyrin IX –> Heme by inserting Fe++
Catalyzed by Ferrochelatase

46
Q

Transferrin

A

Carrier protein in serum

47
Q

How many iron does one transferrin carry?

A

2 Fe++ to cytoplasmic membrane of developing RBC

48
Q

Once transferrin crosses RBC membrane, what occurs next?

A

Fe inserted into protoporphyrin IX
OR
Stored as ferritin or hemosiderin

49
Q

Iron storage forms

A

Ferritin
Hemosiderin

50
Q

What can cause iron deficiency anemia

A

Heme synthesis stops at protoporphyin
Insufficient hgb, small RBC

51
Q

Porphyrias

A

Congenital defects of heme synthesis enzymes

52
Q

Substrates

A

Accumulate
Prior to defect

53
Q

Products

A

Insufficient
After defect

54
Q

What can cause defects in heme synthesis

A

Congenital defects/Porphyrias
Lead poisoning

55
Q

Accumulated substrates can cause what problems

A

Photosensitivity
Neuropathy
Red urine

56
Q

Where does globin synthesis occur

A

On ribosomes

57
Q

When does globin synthesis occur

A

Same time as heme synthesis

58
Q

What stimulates globin synthesis

A

The presence of heme

59
Q

Globin chains in an adult

A

Alpha
Beta
Delta
Gamma

60
Q

Globin chains in embryo

A

Zeta
Epsilon

61
Q

Each molecule of hemoglobin moiety

A

4 heme
2 globin chains (one type)
2 globin chains (another type)

62
Q

Normal adul hemoglobin’s contain what globin chains

A

2 alpha
2 of either B, Y, d

63
Q

Normal adults have a mixture of what types of hemoglobin

A

Hgb A1
Hgb A
Hgb F

64
Q

Hgb A1 is composed of

A

a2 B2

65
Q

What percent of hgb is A1? In an adult

A

92-95%

66
Q

Hgb A1 subset

A

Glycosylated Hgb (aka Glycated Hgb)

67
Q

How does Glycosylated/Glycated Hgb appear?

A

a2B2 + Glucose attached somewhere

68
Q

Where is the glucose attached on Hgb A1c?

A

N-terminus of the beta chain

69
Q

How long does the glucose remain attached to HgbA1c beta chain?

A

The rest of the RBCs life
Irreversible

70
Q

What is an excellent indicator of long term blood glucose levels

A

Hgb A1c

71
Q

What percent of total A1 hgb is hgbA1c?

A

4-6%

72
Q

What is Hgb A2 comprised of?

A

a2 d2

73
Q

What percent of total hgb in a normal adult is a2d2?

A

2-3% of total hgb in a normal adult

74
Q

Hgb F composition

A

a2 Y2

75
Q

What percent of Hgb is HgbF in a normal adult?

A

1-2%

76
Q

Alpha gene on chromosome 16 –>

A

Alpha chain of 141 aa

77
Q

Beta gene on chromosome 11 –>

A

beta chain of 146 aa

78
Q

What can lead to an abnormal hemoglobin?

A

The substitution of even ONE amino acid

79
Q

Where are embryonic hemoglobins detectable?

A

Yolk sac and liver

80
Q

When should embryonic hemoglobins be undetectable?

A

~3 months gestation

81
Q

Gower 1

A

Z2 e2

82
Q

Gower 2

A

a2 e2

83
Q

Portland

A

Z2 Y2

84
Q

Hemoglobin F

A

a2 Y2

85
Q

What percent of fetal hemoglobin if Hgb F?

A

90-95%

86
Q

What form of hgb has higher oxygen affinity than A1?

A

HgbF

87
Q

When does Hgb A1 synthesis begin?

A

~35 weeks gestation

88
Q

How long does residual Hgb F production remain?

A

For life

89
Q

When does adult pattern of hemoglobins appear?

A

1 year of age

hematology (12 decks)

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