Chapter 4 - HEMOGLOBIN (Functions, Components, Synthesis, Types, Forms) Flashcards
Respiratory pigment found in the red cells
HEMOGLOBIN
A conjugated protein synthesized in the RBCS
HEMOGLOBIN
It represents more than 1% of the total body weight and It occupies 28% of the red cell mass.
HEMOGLOBIN
HEMOGLOBIN Function:
Transports oxygen from the lungs where the oxygen tension is high, to the tissues, where the oxygen tension is low.
HEMOGLOBIN also binds to other substances such as (?).
hydrogen ions (which determine pH of the blood), carbon dioxide and 2,3 diphosphoglycerate (2,3-DPG)
These substances do not bind to hemoglobin at the oxygen-binding sites, however, binding of these substances to hemoglobin affects the (?).
affinity of hemoglobin to oxygen
Conversely, binding of (?) causes changes in the structure of the hemoglobin molecule thus affecting its ability to bind other gases or substances
oxygen to hemoglobin
How is CO2 transported in the blood (plasma and red cells?)
As CO2 enters the blood, it combines with H2O to form (?), a relatively weak acid, which dissociates into (?).
carbonic acid (H2CO3)
H+ and HCO3 -
Blood acidity is minimally affected by the released (?)because blood proteins, especially hemoglobin, are effective buffering agents.
H+ ions
The conversion of CO2 to H2CO3 is catalyzed by (?), an enzyme present inside the RBCs.
carbonic anhydrase
Because the enzyme is present only in the RBCs, (?) accumulates to a much greater extent within the red cells than in the plasma.
HCO3
The capacity of blood to carry (?) - is enhanced by an ion transport system inside the RBC membrane that simultaneously moves a HCO3 - out of the cell and in exchange for a chloride ion.
CO2 as HCO3
The simultaneous exchange of these 2 ions, known as the (?), permits the plasma to be used as a storage site for bicarbonate without changing the electrical charge of either the plasma or the red blood cell.
chloride shift
is a curve that plots the proportion of hemoglobin in its saturated form on the Y axis against the prevailing oxygen tension on the X axis.
oxygen dissociation curve/oxyhemoglobin dissociation curve (ODC)
This relates oxygen saturation and partial pressure of O2 in the blood (PO2)
oxygen dissociation curve/oxyhemoglobin dissociation curve (ODC)
determined by hemoglobin affinity for oxygen.
oxygen dissociation curve/oxyhemoglobin dissociation curve (ODC)
Explain the influence/effect of Bohr effect, Haldane effect, 2, 3, DPG and chloride on the affinity of hemoglobin to oxygen
Blood temp
Blood pH (Bohr Effect)
RBC 2,3 DPG
CO2 (Haldane Effect)
Hb F
Abnormal Hbs
HEMOGLOBIN COMPOSITION:
- 1 Globin
- 4 Heme
inorganic iron groups that assist in binding O2
Heme
each iron atom can bind and then release an oxygen molecule
Heme
nitrogenous substance formed in the mitochondrion
Protoporphyrin IX
a salt produced in the Rapoport-Luebering shunt in the RBCs.
2,3 Diphosphoglycerate (DPG)
Composed of 2 sets (dimer) of 2 different polypeptide chains
GLOBIN Chains
The spatial arrangement of each alpha-beta pair is symmetrical
GLOBIN Chains
Contacts between the subunits are by means of H-bonds
GLOBIN Chains
Differences in the globin chain relate both to the sequence and to the number of amino acids in the chain.
GLOBIN Chains
141
Alpha
Beta
Delta
Gamma
Epsilon
146
Gower-1
2 zeta 2 epsilon
Gower-2
2 alpha 2 epsilon
Portland
2 zeta 2 gamma
Hb A
2 alpha 2 beta
Hb A2
2 alpha 2 delta
Hb F
2 alpha 2 gamma
TYPES OF HEMOGLOBIN
: Major normal adult hemoglobin (97%)
Hb A1
: Major Hb of the fetus and the newborn
Hb F
Has high affinity to O2
Hb F
Resistant to both acid elution and alkali denaturation
Hb F
After birth, smaller amounts of(?) are produced
HbF
= HbF is less than 8%
6 months
= HbF less than 2%
After age 2 years
= less than 1%
Adults
Accounts for 1.5 % - 3.5 % of normal adult Hb
Hb A2
Increased in some -Thalassemias, hyperthyroidism and in some cases of megaloblastic anemia
Hb A2
= analogue of alpha-chain
zeta chain
= counterpart of the gamma, beta, and delta chains
epsilon chain
EMBRYONIC HEMOGLOBINS
Hb Gower I
Hb Gower II
Hb Portland
FORMS of HEMOGLOBIN
NORMAL
ABNORMAL
Formed when the RBCs pass through the alveolar capillaries of the lungs
Oxyhemoglobin (HbO2)
The O2 is loosely bound and unstable for easier release into the tissues
Oxyhemoglobin (HbO2)
Gives a scarlet red/bright red color
Oxyhemoglobin (HbO2)
Reduced form
Deoxyhemoglobin (HbCO2)
Hemoglobin with CO2 (carbaminohemoglobin)
Deoxyhemoglobin (HbCO2)
Gives a dark red color
Deoxyhemoglobin (HbCO2)
Hemoglobin with CO (affinity of CO to hb is 200 x greater than the affinity of O2)
Carboxyhemoglobin (HbCO)
Imparts a cherry red in color
Carboxyhemoglobin (HbCO)
Absorption wavelength: 576 nm
Carboxyhemoglobin (HbCO)
Critical Value: 5g /100 ml (May cause irreversible tissue changes when increased)
Carboxyhemoglobin (HbCO)
Treatment: administration of hyperbaric O2
Carboxyhemoglobin (HbCO)
Rapid Tests for HbCO :
- NaOH test: red color
- Dilution test (addition of water): cherry red
- Tannic Acid test: red precipitate
: red color
: cherry red
: red precipitate
- NaOH test
- Dilution test (addition of water)
- Tannic Acid test
Iron (Fe++) is oxidized into its Fe+++ form
Methemoglobin/Hemiglobin (Hi)
Normally makes up 1.5%
Methemoglobin/Hemiglobin (Hi)
Approximately 0.5% - 3% of the total body Hb is spontaneously converted to Hi daily
Methemoglobin/Hemiglobin (Hi)
Conveys a chocolate brown color
Methemoglobin/Hemiglobin (Hi)
Absorption wavelength: 630 635 nm
Methemoglobin/Hemiglobin (Hi)
Methemoglobin/Hemiglobin (Hi)
Screening tests:
Aeration: blood retains its color
Addition of 1% MB: blood turns red
Maintenance of Hemoglobin in the Normal Reduced state (Fe++):
Production of
reduced (?) in the presence of methemoglobin reductase (diaphorase)
reduced (?) in the presence of Glucose-6-PO4 dehydrogenase
(?) and its associated enzymes
Diphosphopyridine dinucleotide (DPNH)
Triphosphopyridine nucleotide (TPNH)
Glutathione
: blood retains its color
: blood turns red
Aeration
Addition of 1% MB
Conditions of Methemoglobinemia:
: commonly attributed to NADH-Methemoglobin reductase deficiency/Diaphorase deficiency
a. Inherited (enzyme deficiency)
: results of various amino acid substitutions in the globin chain that directly affect the heme group.
b. Inherited M
: effects of chemical or therapeutic agents (aniline dyes, nitrate-rich water and foodstuffs)
c. Acquired
Formed when organic sulfides combine with Hb
Sulfhemoglobin (SHb)
Observed in patients taking in oxidant drugs (phenacetin & acetanilid, sulfonamides)
Sulfhemoglobin (SHb)
Irreversible once formed
Sulfhemoglobin (SHb)
NOT normally present in the blood
Sulfhemoglobin (SHb)
Imparts a greenish color
Sulfhemoglobin (SHb)
Absorption wavelength: 600 - 620 nm
Sulfhemoglobin (SHb)
Reference Values for Hemoglobin
Male:
Female:
At Birth:
140 175 g/L
123 153 g/L
150 200 g/L
Increased Hb
Polycythemia Dehydration
Decreased Hb
All anemia
Leukemia
Oligochromia
Physiologic Variations:
After 50 years of age = (?)
Higher in the (?) and lower in the (?)
Lower if (?)
Increased in (?); high altitude
slight decrease
morning; evening
lying down
smokers
Other forms of Hemoglobin:
Formed when ferricyanide is added to the Fe++ of a normal Hb
Cyanmethemoglobin
The most stable among the Hb pigments
Cyanmethemoglobin
Absorption wavelength: 540 nm
Cyanmethemoglobin
What are the glycosylated hemoglobins?
is elevated 2 3 folds in patients with diabetes mellitus.
Hb AIc
It is used as an index of metabolic control in diabetes during the preceding 2 - 3 mons.
Hb AIc
Disorders Related with Abnormal Hemoglobins
diverse group of genetic disorders characterized by a primary, quantitative reduction in globin chain synthesis for hemoglobin.
THALASSEMIA
- Silent carrier
Alpha Thalassemia
- Thalassemia trait/A-Thal minor
Alpha Thalassemia
- Hb H disease
Alpha Thalassemia
- Barts Hdrops fetalis
Alpha Thalassemia
- Beta Thalassemia Major/Cooles anemia
Beta Thalassemias
- Beta Thalassemia Intermedia
Beta Thalassemias
- Beta Thalassemia Minor/Cooles trait
Beta Thalassemias
conditions characterized by qualitative structural abnormalities of the globin polypeptide chains that result from alteration of the DNA genetic code for those chains
HEMOGLOBINOPATHIES
Structural abnormalities may involve amino acid
HEMOGLOBINOPATHIES
HEMOGLOBINOPATHIES (hemoglobin variants)
- Substitution
- Deletion
- Fusion
- Elongation
Examples with Nomenclature:
- Substitution
- Deletion
- Fusion
- Elongation
The most well-known hb variant characterized by substitution of glutamic acid by valine on the 6th amino acid posiion of he b-chain.
Hb S (Sicking hb)
What are the effects of the glutamic acid substitution by valine on the 6th position of the β-chain in the Hb S molecule?
Read the sickle cell crises. Be able to enumerate and discuss them.
FUNCTIONAL CLASSIFICATION OF HEMOGLOBIN VARIANTS
Hb M Boston a258Tyrb2
Hemoglobins associated with methemoglobinemia and cyanosis
Hb M Iwate 287Tyr2
Hemoglobins associated with methemoglobinemia and cyanosis
Hb M Saskatoon 2263Tyr
Hemoglobins associated with methemoglobinemia and cyanosis
Hb M Milwaukee 2267Glu
Hemoglobins associated with methemoglobinemia and cyanosis
Hb M Hde Park 2292Tyr
Hemoglobins associated with methemoglobinemia and cyanosis
Hb FM Osaka 2263Tyr
Hemoglobins associated with methemoglobinemia and cyanosis
Hb FM Fort Riple 2292Tyr
Hemoglobins associated with methemoglobinemia and cyanosis
Hb Chesapeake 292Leu2
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb J Capetown 292Gln2
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Malmo 2297Gln
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Yakima 2299His
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Kempse 2299Asn
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Y psi (Ypsilanti) 2299Tyr
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Hiroshima 22146Asp
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Rainier 22145Cys
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Bethesda 22145His
Hemoglobins associated with Increased Oxygen affinity and polycythemia
Hb Kansas 22102Thr
Hemoglobins associated with Decreased Oxygen affinity and polycythemia
Hb Titusville 294Asn2
Hemoglobins associated with Decreased Oxygen affinity and polycythemia
Hb Providence 2282Asn
Hemoglobins associated with Decreased Oxygen affinity and polycythemia
Hb Agenogi 2290Lys
Hemoglobins associated with Decreased Oxygen affinity and polycythemia
Hb Beth Israel 22102Ser
Hemoglobins associated with Decreased Oxygen affinity and polycythemia
Hb Yoshiuka 22108Asp
Hemoglobins associated with Decreased Oxygen affinity and polycythemia
Hb Bibba 2136Pro2
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Hammersmith 2242Ser
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Bristol 2267Asp
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Olmsted 22141Arg
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Torino 243Val2
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Ann Arbor 280Arg2
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Genova 2228Pro
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Shepherd’s Bush 2274Asp
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Koln 2298Met
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Wein 22130Asp
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb L-Ferrara 247Gly2
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Hasharon 247His2
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Leiden 226 or 7 (Glu deleted)
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Freiburg 2223 (Val deleted)
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Louisville 2242Leu
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Seattle 2270Asp
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Zurich 2263Arg
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Gun Hill 2291-97 (5 a. a. deleted)
Hb may precipitate as Heinz bodies after splenectomy: “congenital Heinz body anemia”
Hb Bart’s 4
Tetramers of normal chains
Hb H 4
Tetramers of normal chains
Hb S (Sicking hb)
Substitution
Hb Gun Hil
Deletion
Hb Constant Spring
Elongation
Hb Lepore-Baltimore
Fusion