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Hematology > Ch. 10 - Hemoglobin Metabolism > Flashcards

Ch. 10 - Hemoglobin Metabolism Flashcards

0
Q

Technique used to describe the structure of hemoglobin

A

X-ray crystallography

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1
Q

First protein whose structure was dexribed using x-ray crystallography

A

Hemoglobin

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2
Q

How many heme groups are in a hemoglobin molecule?

A

4 heme groups

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3
Q

How many polypeptide chains are in a hemoglobin molecule?

A

2 heterogenous pairs

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4
Q

Approximate concentration of hemoglobin in RBCs

A

34 g/dL

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5
Q

Molecular weight of Hb

A

64,000 D

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6
Q

Main function of Hb

A

To transport oxygen from the lungs to tissues

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7
Q

4 atoms in the heme structure

A

Carbon, hydrogen, nitrogen and ferrous iron

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8
Q

Ring of carbon, hydrogen and nitrogen atoms in the heme structure

A

Protoporphyrin IX

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9
Q

What do you call the structure that results when ferrous iron is attached to the carbon, hydrogen and nitrogen ring of the heme structure?

A

Ferroprotoporphyrin

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10
Q

How many oxygen molecules can 1 heme molecule carry?

A

1 oxygen molecule

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11
Q

What specific characteristic of heme renders the blood red?

A

Double bonds

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12
Q

How many helices are there in a globin chain?

A

8 helices

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13
Q

How many nonhelical segments are present in a globin chain?

A

7 nonhelical segments

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14
Q

Primary structure of the Hb molecule

A

Amino acid sequence of the polypeptide chains

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15
Q

Secondary structure of the Hb molcule

A

Chain arrangements in helices and nonhelices

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16
Q

Tertiary structure of the Hb molecule

A

Arrangement of the helices into a pretzel-like configuration

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17
Q

Describe the placement of the heme group in the globin chain

A

The heme group is suspended between the E and F helices. The iron atom is positioned between two histidine radicals, forming a proximal histidine bond with F8 and distal histidine bond with E7.

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19
Q

Which side of the globin chain is hydrophobic?

A

Inside

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20
Q

Which side of the globin chain is hydrophilic?

A

Outside

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21
Q

Quaternary structure of Hb

A

Tetrameric molecule (4 heme groups, 4 polypeptide chains, which may carry 4 oxygen molecules)

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22
Q

Where does heme biosynthesis take place?

A

Mitochondria and the cytoplasm of bone marrow RBC precursors

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23
Q

What RBC precursors are capable of heme biosynthesis?

A

Pronormoblasts, basophilic normoblast, polychromatic normoblasts, orthochromic normoblasts and polychromatic erythrocytes

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24
Q

Plasma protein that carries iron in the ferric (Fe3+) form to developing RBCs

A

Ferritin

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25
Q

What chromosome number are the alpha and zeta genes contained?

A

Chromosome 16

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26
Q

What chromosome number are the beta, gamma, epsilon and delta genes contained?

A

Chromosome 11

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27
Q

What genes are contained in chromosome 16?

A

Alpha and zeta genes

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28
Q

What genes are contained in chromosome 11?

A

Beta, gamma, epsilon and delta

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29
Q

How many genes are there for the alpha and gamma genes?

A

4 genes per person

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30
Q

What RBC precursors produce globin chains?

A

Pronormoblasts, basophilic normoblasts, polychromatic normoblasts, orthochromic normoblasts and polychromatic erythrocytes

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31
Q

Where does globin chain synthesis take place?

A

Inside RBC precursors

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32
Q

Which globin protein is present in excess in pronormoblasts?

A

Alpha-globulin

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33
Q

Which globin protein is translated more efficiently during globin biosynthesis?

A

Beta-globulin

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34
Q

Predominant Hb in postnatal life

A

Hb A

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35
Q

Globin chains in Hb A

A

2 alpha and 2 beta chains

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36
Q

Globin chains in Hb A2

A

2 alpha and 2 delta chains

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37
Q

Globin chains in Hb F

A

2 alpha and 2 gamma chains

38
Q

RBCs with Hb F

A

F cells

39
Q

Dominant Hb during birth

A

Hb F

40
Q

What are the 4 embryonic Hb chains?

A
  • alpha
  • gamma
  • epsilon
  • zeta
41
Q

Globin chains of Gower-1 Hb

A

2 zeta and 2 epsilon chains

42
Q

Globin chains of Gower-2 Hb

A

2 alpha and 2 epsilon chains

43
Q

Globin chains of Portland Hb

A

2 zeta and 2 gamma chains

44
Q

Types of Hb present during intrauterine period

A

Gower-1, Gower-2, Portland and F

45
Q

Types of Hb present at birth

A

Hb F and A

46
Q

Types of Hb present during adulthood

A

Hb A, A2 and F

47
Q

Posttranslational modification formed by nonenzymatic binding of various sugars with globin chain amino groups

A

Glycation

48
Q

Most glycated hemoglobin

A

Hb A1C

49
Q

Describe the glycation of Hb A1C

A

Glucose attaches to the N-terminal valine of the beta chain

50
Q

What does increased Hb A1C indicate?

A

Uncontrolled diabetes mellitus

51
Q

What is the rate-limiting step in heme synthesis?

A

The initial reaction of glycine and succinyl CoA to from ALA, catalyzed by ALAS (aminolevulinate synthase)

52
Q

What process regulates globin production?

A

The rate at which the DNA is transcribed to mRNA

53
Q

Stimulates hemoglobin synthesis

A

Tissue hypoxia

54
Q

Reference interval for Hb (men)

A

14-18 g/dL (140-180 g/L)

55
Q

Reference interval for Hb (women)

A

12-15 g/dL (120-150 g/L)

56
Q

Reference interval for Hb (newborns)

A

16.5-21.5 g/dL (165-215 g/L)

57
Q

What is the function of Hb

A

To bind oxygen molecules in the lungs (requires high oxygen affinity), to transport oxygen and to efficiently unload oxygen to the tissues (requires low oxygen affinity)

58
Q

Approximately how much of oxygen is bound by 1 gram of Hb?

A

1.34 mL

59
Q

Affinity of Hb for oxygen

A

PO2 (partial pressure of oxygen)

60
Q

The amount of oxygen needed to saturate 50% of Hb

A

P50 value

61
Q

Shape of normal oxygen dissociation curve

A

Sigmoidal

62
Q

Shift in the oxygen dissociation curve due to pH

A

Bohr effect

63
Q

The normal PO2 that results to 50% oxygen saturation of the Hb molecule

A

27 mm Hg

64
Q

Reference interval for arterial oxygen saturation

A

96-100%

65
Q

Presence of what substance induces the Hb molecule to change from a relaxed oxygenated molecule to a tense deoxygenated molecule?

A

2,3-bisphosphoglycerate

66
Q

What subtance stabilizes the T structure of Hb?

A

Salt bridges

67
Q

What happens when the salt bridges are broken?

A

The Hb molecule is able to bind to oxygen

68
Q

3 substances that decrease the affinity of Hb for oxygen by strengthening the salt bridges that lock the molecule into its T conformation

A
  • carbon dioxide
  • hydrogen ions
  • chloride ions
69
Q

Release of myoglobin into the plasma when there is damage to the muscle in myocardial infarction, trauma or severe muscle injury

A

Rhabdomyolysis

70
Q

Explain why fetal Hb conc is high

A

Since Hb F delivers oxygen less readily to tissues, its concentration should be high to achieve adequate tissue oxygenation.

71
Q

Describe the reaction of carbon dioxide in the blood

A

Carbon dioxide combines with water facilitated by carbonic anhydrase to form carbonic acid. Carbonic acid then dissociates to release hydrogen ion and bicarbonate.

72
Q

What type of Hb results when CO2 is bound to the N-terminal amino group of the globin chain?

A

Carbaminohemoglobin

73
Q

Type of Hb variant that contains iron in the oxidized or ferric state (Fe3+)

A

Methemoglobin

74
Q

What shift is produced by increased amounts of methemoglobin?

A

Left shift

75
Q

What type of Hb variant is present with patients who inherit Hb M disease?

A

Methemoglobin

76
Q

What is the peak range for methemoglobin?

A

620-640 nm at pH 7.1

77
Q

What Hb variant does not cause a shift in the oxygen dissociation curve?

A

Sulfhemoglobin

78
Q

Color of methemoglobin

A

Brownish to bluish

79
Q

Color of sulfhemoglobin

A

Greenish

80
Q

How is sulfhemoglobin formed?

A

By the irreversible oxidation of Hb by sulfonamides, phenacitin, acetanilide or phenazopyridine

81
Q

How is carboxyhemoglobin formed?

A

By the combination of carbon monoxide with heme iron

82
Q

Reference interval for carbon monoxide

A

0.2-0.8%

83
Q

Treatment for carboxyhemoglobin

A

Hyperbaric oxygen

84
Q

Wavelength at which carboxyhemoglobin is detected

A

541 nm

85
Q

Wavelength where sufhemoglobin is at its peak

A

620 nm

86
Q

Technique used to separate the different types of Hb such as Hb A, A2 and F

A

Hemoglobin electrophoresis

87
Q

The reference method for hemoglobin assay

A

Cyanmethemoglobin method

88
Q

Used to convert hemoglobin to SLS-hemoglobin. Does not generate toxic wastes

A

Sodium Lauryl Sulfate (SLS)

89
Q

Compensatory organ for respiratory problems

A

Kidneys

90
Q

Compensatory organs for metabolic problems

A

Lungs followed by kidneys

91
Q

Ultimate guardian of homeostasis

A

Kidneys

92
Q

What part of the globin chain swings in and out of position to permit the passage of oxygen into and out of the Hb molecule?

A

Distal histidine

Hematology (7 decks)

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