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Hematalogy Lecture > Hemoglobin and iron metabolism > Flashcards

Hemoglobin and iron metabolism Flashcards

1
Q

 What is the Relationship between hemoglobin and heme? 

A

Hemoglobin contains heme

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2
Q

Is a conjugated globular proteins which constitutes 33% of RBC weight by volume

A

Hemoglobin

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3
Q

What is the weight percentage of hemoglobin in RBCs?

A

33%

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4
Q

_____% of hemoglobin synthesis occurs during nucleated stages of maturation

____% occurs during the reticulocyte stage

A

66

33

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5
Q

One hemoglobin molecule contains….

A

-two pairs of two different polypeptide chains (dimers) ie: 4 globin chains arranged as a tetramer
-Four molecules of protoporphyrin IX
-For iron atoms (Fe2+) that combine with protoporphyrin IX to form 4 heme rings
-one 2,3-BPG molecule (from RLP pathway) may or may not occupy the center of the entire hemoglobin molecule

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6
Q

what does 2,3-BPG help with?

A

Oxygen offloading

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7
Q

Normal hemoglobin production is dependent upon what three processes?

A

• adequate iron delivery and supply
• Adequate synthesis of protoporphyrins
• Adequate globin (to hold iron and heme) synthesis

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8
Q

Apo….

A

Vacant of iron

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9
Q

Fe has extremely ____ Bioavailability in food.

A

Low

*10-20 mg of iron/day, only 1-2 mg is absorbed

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10
Q

How does the body compensate for low bioavailability of iron? 

A

Recycles iron from degraded RBCs (Which has been stored in splenic macrophages) 

-no mechanism for excretion

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11
Q

about _____ of iron is in storage form - ferritin or hemosiderin in macrophages (very small amount in transferrin (Plasma carrier protein))

A

1/4

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12
Q

Where is iron stored? 

A

In macrophages in the spleen

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13
Q

Is ferritin or hemosiderin easier to use? 

A

Ferritin

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14
Q

Ferritin is made of a cylindrical protein called ______________, Plus the many iron atoms stuffed into it

A

Apoferritin

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15
Q

Apoferritin + Fe =

A

Ferritin

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16
Q

What is Apoferritin?

A

Ferritin without iron

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17
Q

When Fe is needed, _____ is released from ferritin and guts mucosal cells, this Fe Attaches to a special Fe transport proteins called transferrin.

A

Fe3+ (needs to be in this form)

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18
Q

Fe transport Protein

A

Transferrin 

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19
Q

Transparent can transport up to _____ Fe3+ Simultaneously through the plasma; It delivers Fe3+ into RBCs 

A

2 atoms

-transferrin is returned to cell surface for recycling
-Fe3+ is reduced to ferrous (Fe2+) in cytoplasm of RBC

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20
Q

A plasma proteins that transports ferric iron (Fe3+) to the developing RBCs

A

Transferrin

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21
Q

Iron (ferrochelatase) is actively carried across the RBC membrane to the mitochondria, where it is matched with _______________ to make heme. 

A

Protoporphyrin IX

He leaves the mitochondria and travels to the cytosol (Cytoplasm) To join the globin chains 

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22
Q

Protoporphyrin synthesis:

Begins with _______________
-By-product of the tricarboxylic acid cycle

A

succinyl coenzyme-A (COA)

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23
Q

Protoporphyrin synthesis:

CoA combines with glycine to form ______________

Where does it occur?

A

aminolevulinic acid
(ALA)

Mitochondria of pronormoblast and requires B6

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24
Q

Protoporphyrin synthesis:

ALA and ALA dehydrates combine to form __________.

A

Prophobilinogen (PBG)

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25
Q

Protoporphyrin synthesis:

Pathway continues until protoporphyrin IX Combines with _______________ to make heme. 

A

Ferrochelatase/heme synthase

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26
Q

The globin genes are transcribed into ______ In the nucleus of an immature (& still nucleated) RBC

A

mRNA

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27
Q

Chromosome 16 contains the ________ and _______ Globin genes. 

A

Alpha and Zeta (16 AZ) 

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28
Q

Chromosome 11 contains the _______ Globin genes and all others.

A

Beta (11B)

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29
Q

In Cytoplasm, mature mRNA transcript is translated at a __________ Into a polypeptide chain, which immediately begins to assume it’s secondary confirmation (And then it’s tertiary and then quaternary shapes) 

A

Ribosome

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30
Q

Refers to linear amino acid structure (Beads on a string). The amino acid in a polypeptide chain are numbered beginning with number one at the N(amino) Terminal, and ending at C – terminal

A

Primary hemoglobin structure (chain) 

  • changes to secondary very quickly
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31
Q

Refers to the polypeptide chain arrangement in helical‘s and non-helical‘s.

A

Secondary structure

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32
Q

Of the secondary structure each chain is divided into _____ helicals and ____ nonhelical segments.

A

8, 7

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33
Q

The helices are separate and structurally rigid segments, designated by the letters ______ through ______. 

A

A, H

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34
Q

The non-helical segments are more _________ and lie between helical segments. This arrangement for a slight but real physical bending of the polypeptide chain

A

Flexible

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35
Q

This structure is it involves bending of non-helical. Refers to the roughly globular shape (like a pretzel)  that the secondary level of structure assumes spontaneously due to non-hydrogen bonds (such as sulfhydryl bridges) Formed between neighboring amino acid side chains

A

Tertiary Hemoglobin structure

(hold heme ring into these pockets)

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36
Q

At what point is one heme group inserted inside each of the four globin chains?

A

Tertiary structure

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37
Q

This structure refers to tetramer formed by association of two pairs of polypeptide chains

A

Quaternary structure

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38
Q

Quaternary structure:

Complete hemoglobin molecule is spherical, has ______ Heme groups attached to ______ Polypeptide chains, and can carry ______ Molecules of oxygen.

A

4, 4, 4

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39
Q

globin chains are assembled from…

A

Two pairs of polypeptide chains (Four chains per hemoglobin molecule)

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40
Q

What are the four primary chains that can be produced? 

A

Alpha, beta, gamma, delta

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41
Q

 many hemoglobin forms can be formed depending upon…

A

The combination of the two pairs of globin chains

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42
Q

What is fetal hemoglobin (F) composed of? And in what proportions? 

A

Two alpha and two gamma (AG)

Newborns- 80%
Adults- <1%

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43
Q

What is A1 hemoglobin composed of? And in what proportions?

A

Two alpha and two beta (AB)

Newborn- 20%
Adult-97%

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44
Q

What is hemoglobin A2 composed of? And in what proportions?

A

Two alpha and two delta (AD)

Newborn- <0.5%
Adult- 2.5%

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45
Q

During the first three months after conception, embryo produces what three embryonic hemoglobins?

A

Portland, Gower 1, and Gower 2

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46
Q

What globin chains is Portland composed of?

A

Zeta 2, gamma 2 (GZ)

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47
Q

What globin chains is Gower I composed of?

A

Zeta two, epsilon two

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48
Q

What globin chains is Gower II composed of?

A

Alpha two, epsilon two (AE)

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49
Q

When does fetal hemoglobin begin to be produced?

A

In the second trimester, Hepatic phase 

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50
Q

By birth, hemoglobin-F comprises about ______% of total hemoglobin with the remainder being hemoglobin A1

A

80

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51
Q

When is essentially all of a child’s Hemoglobin in the adult forms?

A

 by the first birthday

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52
Q

Hemoglobin can be modified by ___________ Binding of various sugars with the globin chains. What is the most common?

A

Non-enzymatic

Hgb A1c

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53
Q

a glycosylated hemoglobin that can tell how well diabetes is being managed. Glucose attaches to the N-terminal valine of the beta chain

A

Hgb A1c

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54
Q

What cells typically contain more hemoglobin A1C? What percentage is normal? 

A

Older cells (4-6% of Hgb A)

*increased with diabetes! (proportional to the mean glucose level over 2 to 3 months)

55
Q

What is the main mission of RBCs?

A

• contain, transport, and protect hemoglobin molecules so that oxygen can be carried

56
Q

Each hemoglobin molecule consists of ______ Globin chains and ______ heme groups, Each with a center iron molecule

A

4, 4

57
Q

Each globe and chain has a ______________”pocket” Containing a heme group 

A

Hydrophobic (Protects heme and keeps it in the Fe2+ form)

58
Q

The iron from each heme is directly bonded to ____________ Of the globin chain

A

2 histidines 

59
Q

What is the function of proximal histidine?

A

To increase the oxygen affinity of the heme ring

60
Q

What is the function of distal histidine?

A

To protect the iron in the ferrous state (hydrophobic pocket) Which diminishes the binding of carbon monoxide (CO)

  • The exterior of the chain is hydrophilic which makes the molecule soluble
61
Q

What is the first step of hemoglobin molecule assembly?

A

A Ferric (Fe3+) Fe Molecule (Originally obtained from ferritin, but being transported by transferrin) Is chemically reduced to the ferrous (Fe2+) Form in the nucleated RBC cytoplasm

62
Q

Second step of hemoglobin molecule assembly?

A

Fe2+ is transported into mitochondrion and inserted into center of a protoporphyrin IX molecule (At this point the molecule can be called heme)

63
Q

Protoporphyrin IX + Fe =

A

Heme

64
Q

Step three of hemoglobin molecule assembly

A

Finished heme is released from the mitochondria back into the cytoplasm

65
Q

Step four of hemoglobin molecule assembly

A

In the cytosol, finished alpha and beta globin polypeptide chains are released from nearby Ribosomes

66
Q

Step five of hemoglobin molecule assembly

A

One heme molecule is inserted into each globin polypeptide

67
Q

Step six of Hemoglobin molecule assembly

A

Alpha and beta chains quickly form dimers and then dimers quickly form a tetramer (4° Structure) 

68
Q

Step seven of hemoglobin molecule assembly? 

A

One 2,3-BPG/DPG molecule is inserted into the central cavity of each finished hemoglobin molecule as needed

69
Q

When Fe is low, [FEP] goes _____.

A

Up

70
Q

What to test measure Excess protoporphyrin Left over in mitochondria when iron supply is diminished. It becomes complex to zinc, then shipped out into cytoplasm 

A

FEP (Free Erythrocyte Protoporphyrin)

Zinc Proto-porphyrin

71
Q

What are the three major functions of hemoglobin

A

• transport of oxygen
• Transport of CO2
• Buffering the blood

72
Q

What are the allosteric affects of hemoglobin?

A

• cooperative binding binding of oxygen
• regulation of oxygen affinity by 2,3-BPG
•Bohr effect 

73
Q

The binding of one O2 molecule causes it increased infinity of the other heme groups for additional O2 molecules. What is this called?

A

Heme-heme interaction

74
Q

The more O2 hemoglobin binds, the ___________ it’s Affinity for O2 becomes

A

Greater

75
Q

At any time a heme molecule may be carrying ___________ O2 molecules. As O2 binds to a heme group, that heme group shifts slightly, and this overall shape change then encourages another oxygen molecule to bind to another nearby heme. 

A

1, 2, 3, or 4

76
Q

Hemoglobin saturated with O2

A

Oxyhemoglobin

77
Q

Hemoglobin without bound O2

A

Deoxyhemoglobin

78
Q

Hemoglobin with CO2

A

Carbaminohemoglobin

79
Q

Hemoglobin with CO2 bound

A

Carboxyhemoglobin

80
Q

oxygen __________ occurs in tissues and is regulated, in part, by the oxygen affinity of hemoglobin

A

Tension

(you get tense when you need oxygen) 

81
Q

Oxygen _________ occurs in the RBC and is modulated by the concentration of phosphates in cell

A

Affinity

-in areas of Hypoxic tissue, as oxygen moves from Hemoglobin into the tissues, the amount of reduced hemoglobin decreases resulting in reduced oxygen affinity

82
Q

If tissue hypoxia persists, the depletion of ________ Leads to increased glycolysis and production of more _________, Which will further lower hemoglobin oxygen affinity

A

2,3-BPG (both blanks)

83
Q

What pathway produces 2,3-BPG?

A

RLP

84
Q

This is an allosteric regulator of hemoglobin, which diminishes the affinity of hemoglobin for oxygen

A

2,3-bisphosphoglycerate (2,3-BPG)

85
Q

It binds between beta chains of hemoglobin A1 via salt bridges when hemoglobin is in a more unoxygenated state (aka. Tense or “T” form) 

A

2,3-BPG

86
Q

The binding process of 2,3-BPG moves Beta change slightly further apart and results in a shape change causing _________ O2 Affinity, such that any remaining bound O2 is preferencially “offloaded”into the tissues

A

Decreased

87
Q

Explain the process of relaxed or “R” form

A

What’s the deoxyhemoglobin reaches the lungs, however, the binding of O2 to heme is a greater Force then the weak bonds holding the 2,3-BPG Inside the hemoglobin. As a result hemoglobin A-1 becomes oxygenated (“relaxed” form) and the resulting heme-heme Interaction causes 2,3-BPG to be Expelled

88
Q

 what happens when salt bridges are broken?

A

Beta chains move closer and the shape change then permits further binding of additional O2 molecules. This results in increased O2 uptake and increased oxygen affinity

89
Q

Breaking of the salt bridge allows what to happen?

A

Allows oxygen to be bound

• The salt Bridge keeps 2,3-BPG in place?

90
Q

Tense form equals..
______ 2,3-BPG and
______ oxygen infinity
______ Oxygen offloading (in tissues) 

A

Increased
Decreased
Increased

91
Q

Relaxed form equals…
______ 2,3-BPG
______ Oxygen affinity
______ Oxygen uptake (in lungs)


A

No
Increased
Increased

92
Q

What contributes to hemoglobins ability to bind large quantities of oxygen, but also to release oxygen we needed

A

This is a result of the quaternary structure changes

  • look at oxygen disassociation curve
93
Q

The affinity of hemoglobin for O2 depends on the….:

A

Partial pressure of O2 (PO2)

94
Q

What is P50 value?

A

O2 needed to saturate 50% of hemoglobin

95
Q

What does the oxygen disassociation curve plot?

A

Plots the O2 content of hemoglobin (% Saturation) Versus the PO2

(Myoglobin to the left and hemoglobin to the right)

96
Q

A shift to the right of the oxygen disassociation curve is…..

__________ Oxygen affinity

A

Decreased (Tends to offload oxygen)

  • Giveaway 02 with my right hand
97
Q

In hypoxia, where would a shift to the right occur?

A

In the tissues

98
Q

What Can cause a shift to the right on the oxygen disassociation curve?

A

•Increase CO2
• decrease pH
• Increased 2,3-DPG
• Increase in body temperature

99
Q

-Oxygen binding heme protein present in cardiac and skeletal muscle
-greater oxygen affinity than hemoglobin, and not as effective in releasing oxygen to the tissues
-Normally flushed through kidneys
-can be distinguished from Hemoglobinin the urine

A

Myoglobin

100
Q

What are the three methods carbon dioxide is transported from the tissues to the lungs

A

• dissolution directly into the blood (Not often)
• Binding to hemoglobin- carbaminohemoglobin (Not often)
• Carried as a bi carbonate ion (about 75%) 

101
Q

_____ and _____ promote the release of oxygen from the hemoglobin molecule
• Enhances the release of oxygen in tissues

A

H+ and CO2

102
Q

Each red blood cell contains this enzyme that catalyzes the conversion of CO2 (Given up by tissues) and H2O, to produce carbonic acid (H2CO3)

A

Carbonic anhydrase (CA) 

103
Q

In the lungs, binding of oxygen releases H+ and displaces bound _________

A

Hgb-CO2

HCO3- + H ———-> CO2 + H2O

104
Q

About ____% Of the blood CO2 is converted to bicarbonate and H + ions

A

90

105
Q

About ____% of CO2 in arterial blood is physically dissolved in plasma

A

5

106
Q

About ____% of CO2 known as carbaminohemoglobin, Is carried in blood bound to amino groups of plasma proteins.

A

5

107
Q

What are the two ways the amount of oxygen reaching the tissues can be regulated by?

A

• changing the number of circulating RBCs with a change in the rate of erythropoiesis
•Altering the affinity of hemoglobin for oxygen

108
Q

what are the six factors that affect hemoglobin‘s affinity for O2

A

• body temperature
• pH (Bohr effect)
•2,3-BPG/DPG
•CO2
•Fetal Hgb
•Abnormal Hgb Variants 

109
Q

An increase in body temperature will cause _____________ in O2 Solubility. 

A

Decrease

*Helps movement of O2 off hemoglobin 

110
Q

 Phenomenon in which increase pH causes a left shift

A

Bohr effect

*High pH, 02 uptake in hemoglobin is favored

( think “pH is Bohring”) 

111
Q

In the lungs where pH is higher, 02 uptake by hemoglobin is…..

A

Increased

  • PH is lower in the tissues that causes O2 release by hemoglobin
112
Q

2,3-BPG/DPH =tense form = __________ O2 affinity and ___________ 02 offloading. 

A

Decreased, Increased
*in tissues (think tense in the tissues)

113
Q

Phenomenon in which increased CO2 causes right shift, encouraging 02 release (And vice versa)

A

Haldane effect

114
Q

Increased CO2 causes ________ shift, Encouraging 02 release

A

Right

(Haldane effect is due to CO2)

115
Q

 does A1 or F hemoglobin upload O2 more easily? 

A

F hemoglobin

116
Q

How does abnormal hemoglobin variants affect affinity for O2?

A

These Hemoglobin may shift more to the right or to the left than A1 Hgb would

117
Q

carboxyhemoglobin results from the binding of ____ To hemoglobin.

A

CO (not CO2)

118
Q

CEO binds to hemoglobin at a rate of ______X Higher than regular O2. so asphyxiation Results in a matter of minutes
What shift would this cause?

A

200

Left

119
Q

What color is carboxyhemoglobin? 

A

Hallmark cherry red color (Does not offload Easley) 

120
Q

What is the most common source of carboxyhemoglobin?
Death can result when concentrations reach what percentage of normal hemoglobin?

A

Auto exhaust

50-70% (normal is less than 1%)

121
Q

Form of hemoglobin that contains iron in the ferric state (Fe3+)

A

Methmoglobin 

(measured spectrophotometry in whole blood)

122
Q

What is the color of methmoglobin? 
What is it commonly associated with?

A

Brownish to bluish color

Nitrites and genetic disorders

(measured spectrophotometry in whole blood)

123
Q

Accumulation of methmoglobin produces a shift to the ________, Resulting in….

A

Left

oxygen not being delivered efficiently to the tissues

124
Q

What hemoglobin conversion is permanent for the life of the cell and has a green pigment?

A

sulfhemoglobin

(measured spectrophotometry in whole blood)

125
Q

-Formed by the oxidation of hemoglobin by drugs or chemicals
-displays 100 times less affinity for oxygen then unmodified hemoglobin

A

Sulfhemoglobin (usually from sulfa drugs) 

126
Q

In extravascular hemolysis, hemoglobin is broken down into….

A

Heme, iron, and globin 

127
Q

Extravascular hemolysis:
Heme iron is stored as __________ or __________ within macrophages until needed ——> transferrin and cycle Continues. 80% of transferrin
-Globin is broken down and returns to the amino acid pool

A

Ferritin, hemosiderin

128
Q

Extravascular hemolysis:
Component of heme converts to bilirubin (released into the plasma and excreted by the liver in bile) 

A

Protoporphyrin

129
Q

Extravascular hemolysis:
Is exsecreted from the liver into the small intestine via the bile duct where it is converted by bacterial flora to urobiligen

A

Conjugated bilirubin

130
Q

Most urobilinogen is excreted in the stool as _________. 10% to 20% is reabsorbed by the gut. 

A

Urobilin

131
Q

With liver disease, the enterohepatic cycle is impaired and increased amounts of ____________ Is excreted in the urine. 

A

Urobilinogen

132
Q

In intravascular hemolysis cell contents are released into the plasma. ____________ and ___________ work to salvage they released hemoglobin, so the iron is not lost.
They carry the hemoglobin to the liver, where it is broken down to bilirubin. 

A

Haptoglobin, hemopexin

133
Q

A decrease in serum __________ may be used to indicate intravascular hemolysis.

If haptoglobin is depleted, free hemoglobin is filtered by the renal glomerulus. 

A

Haptoglobin

Hematalogy Lecture (35 decks)

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