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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
What chromosome number are the alpha and zeta genes contained?
Chromosome 16
26
What chromosome number are the beta, gamma, epsilon and delta genes contained?
Chromosome 11
27
What genes are contained in chromosome 16?
Alpha and zeta genes
28
What genes are contained in chromosome 11?
Beta, gamma, epsilon and delta
29
How many genes are there for the alpha and gamma genes?
4 genes per person
30
What RBC precursors produce globin chains?
Pronormoblasts, basophilic normoblasts, polychromatic normoblasts, orthochromic normoblasts and polychromatic erythrocytes
31
Where does globin chain synthesis take place?
Inside RBC precursors
32
Which globin protein is present in excess in pronormoblasts?
Alpha-globulin
33
Which globin protein is translated more efficiently during globin biosynthesis?
Beta-globulin
34
Predominant Hb in postnatal life
Hb A
35
Globin chains in Hb A
2 alpha and 2 beta chains
36
Globin chains in Hb A2
2 alpha and 2 delta chains
37
Globin chains in Hb F
2 alpha and 2 gamma chains
38
RBCs with Hb F
F cells
39
Dominant Hb during birth
Hb F
40
What are the 4 embryonic Hb chains?
- alpha - gamma - epsilon - zeta
41
Globin chains of Gower-1 Hb
2 zeta and 2 epsilon chains
42
Globin chains of Gower-2 Hb
2 alpha and 2 epsilon chains
43
Globin chains of Portland Hb
2 zeta and 2 gamma chains
44
Types of Hb present during intrauterine period
Gower-1, Gower-2, Portland and F
45
Types of Hb present at birth
Hb F and A
46
Types of Hb present during adulthood
Hb A, A2 and F
47
Posttranslational modification formed by nonenzymatic binding of various sugars with globin chain amino groups
Glycation
48
Most glycated hemoglobin
Hb A1C
49
Describe the glycation of Hb A1C
Glucose attaches to the N-terminal valine of the beta chain
50
What does increased Hb A1C indicate?
Uncontrolled diabetes mellitus
51
What is the rate-limiting step in heme synthesis?
The initial reaction of glycine and succinyl CoA to from ALA, catalyzed by ALAS (aminolevulinate synthase)
52
What process regulates globin production?
The rate at which the DNA is transcribed to mRNA
53
Stimulates hemoglobin synthesis
Tissue hypoxia
54
Reference interval for Hb (men)
14-18 g/dL (140-180 g/L)
55
Reference interval for Hb (women)
12-15 g/dL (120-150 g/L)
56
Reference interval for Hb (newborns)
16.5-21.5 g/dL (165-215 g/L)
57
What is the function of Hb
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
Approximately how much of oxygen is bound by 1 gram of Hb?
1.34 mL
59
Affinity of Hb for oxygen
PO2 (partial pressure of oxygen)
60
The amount of oxygen needed to saturate 50% of Hb
P50 value
61
Shape of normal oxygen dissociation curve
Sigmoidal
62
Shift in the oxygen dissociation curve due to pH
Bohr effect
63
The normal PO2 that results to 50% oxygen saturation of the Hb molecule
27 mm Hg
64
Reference interval for arterial oxygen saturation
96-100%
65
Presence of what substance induces the Hb molecule to change from a relaxed oxygenated molecule to a tense deoxygenated molecule?
2,3-bisphosphoglycerate
66
What subtance stabilizes the T structure of Hb?
Salt bridges
67
What happens when the salt bridges are broken?
The Hb molecule is able to bind to oxygen
68
3 substances that decrease the affinity of Hb for oxygen by strengthening the salt bridges that lock the molecule into its T conformation
- carbon dioxide - hydrogen ions - chloride ions
69
Release of myoglobin into the plasma when there is damage to the muscle in myocardial infarction, trauma or severe muscle injury
Rhabdomyolysis
70
Explain why fetal Hb conc is high
Since Hb F delivers oxygen less readily to tissues, its concentration should be high to achieve adequate tissue oxygenation.
71
Describe the reaction of carbon dioxide in the blood
Carbon dioxide combines with water facilitated by carbonic anhydrase to form carbonic acid. Carbonic acid then dissociates to release hydrogen ion and bicarbonate.
72
What type of Hb results when CO2 is bound to the N-terminal amino group of the globin chain?
Carbaminohemoglobin
73
Type of Hb variant that contains iron in the oxidized or ferric state (Fe3+)
Methemoglobin
74
What shift is produced by increased amounts of methemoglobin?
Left shift
75
What type of Hb variant is present with patients who inherit Hb M disease?
Methemoglobin
76
What is the peak range for methemoglobin?
620-640 nm at pH 7.1
77
What Hb variant does not cause a shift in the oxygen dissociation curve?
Sulfhemoglobin
78
Color of methemoglobin
Brownish to bluish
79
Color of sulfhemoglobin
Greenish
80
How is sulfhemoglobin formed?
By the irreversible oxidation of Hb by sulfonamides, phenacitin, acetanilide or phenazopyridine
81
How is carboxyhemoglobin formed?
By the combination of carbon monoxide with heme iron
82
Reference interval for carbon monoxide
0.2-0.8%
83
Treatment for carboxyhemoglobin
Hyperbaric oxygen
84
Wavelength at which carboxyhemoglobin is detected
541 nm
85
Wavelength where sufhemoglobin is at its peak
620 nm
86
Technique used to separate the different types of Hb such as Hb A, A2 and F
Hemoglobin electrophoresis
87
The reference method for hemoglobin assay
Cyanmethemoglobin method
88
Used to convert hemoglobin to SLS-hemoglobin. Does not generate toxic wastes
Sodium Lauryl Sulfate (SLS)
89
Compensatory organ for respiratory problems
Kidneys
90
Compensatory organs for metabolic problems
Lungs followed by kidneys
91
Ultimate guardian of homeostasis
Kidneys
92
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?
Distal histidine

Hematology (7 decks)

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