Download MLAB 1315- Hematology Fall 2007 Keri Brophy

MLAB 1315- Hematology
Fall 2007
Keri Brophy-Martinez
Unit 6: Hemoglobin
Hemoglobin
 What is it?
 Iron- bearing protein which is the main component of the RBC
 Gives the red cell its color
 Function
 Carry oxygen from the lungs to the tissues
 Remove CO2
 Buffering action, maintains blood pH as it changes from
oxyhemoglobin (carrying O2) to deoxyhemoglobin ( without O2)
 Life span

120 days
Hemoglobin Normal Range
 Adults


Male 13.5-17.5 g/mL
Female 12.0-16.0 g/mL
 Children


Birth 13.5-20.0 g/mL
6-12 years 11.5-15.5 g/mL
**Refer to inside cover of text for other ranges
Structure
 Structure
 Globin: a tetramer of two pairs of unlike globin polypeptide chains
 2 alpha (α) chains
 2 beta (β) chains
 4 heme groups, each of which contains a protoporphyrin ring plus
Fe ++. Iron can only bind oxygen in the ferrous (Fe++) state.
Structure
Fe++
Heme + Globin = HEMOGLOBIN
Protoporphyrin
Structure
Oxygen Dissociation Curve
 Binding and Release of oxygen from the hemoglobin molecule is
defined by this curve
 Illustrates the qualities of oxygen dissociation and attempts to
graphically demonstrate how the Hgb molecule and oxygen
respond to normal and abnormal physiology
 When the Hgb molecule is fully saturated, it has all its oxygen
needs and an increased level of O2 tension. As it travels from
pulmonary circulation to the venous circulation, the molecule is
more inclined to give up oxygen in response to the needs of the
tissues.
Oxygen Dissociation Curve
 Right-Shift
 Hgb has less attraction
for O2
 Hgb willing to release
O2 to tissue
 Examples: anemia,
acidosis
 Even though there
may be less RBC’s,
they act more
efficiently to deliver O2
to target
Oxygen Dissociation Curve
 Left shift



Hgb has more attraction for O2
Hgb less willing to release O2 to tissue
Examples: presence of abnormal Hgb’s,
alkalosis
Oxygen Dissociation Curve
 Roller Coaster Analogy

As you start to incline, you hold on tight, but as
you roll down the hill, you throw up your arms
and you relax your grip.
Synthesis
 Synthesis
 Occurs in the cytoplasm of developing red cells as they mature in
the bone marrow
 Processes necessary for normal synthesis



Adequate iron supply & delivery
Adequate synthesis of protoporphyrins
Adequate globin synthesis
Synthesis
 Syntheis of hemoglobin in the reticulocyte (retic)

Iron delivery & supply


Iron is delivered to the reticulocyte by transferrin a glycoprotein
synthesized in the liver
Excess iron aggregates in the cytoplasm as ferritin
 Synthesis of protoporphrins




Begins in the mitochondria of the reticulocyte
Mediated by erythropoietin and the presence of vitamin B6
Protoporphyrin + iron = heme
Excess formation of porphyrin results in metabolic disorders called “
porphyrias”
Synthesis
 Globin synthesis

Globin chain synthesis occurs on the ribosomes of the
reticulocyte.
The rate of globin synthesis is proportional to the rate of
porphyrin
synthesis.



Excess accumulated iron in the nucleated RBC (NRBC) results
in a cell called a sideroblast.
A siderocyte is a red blood cell (anucleated) with excess iron
Proper globin synthesis depends on genes. The precise order
of amino acids in the globin chains is critical to the structure
and function of hemoglobin. (More discussion to follow in
another section.)
 Chain designations are as follows
 Alpha α, beta β, delta δ, epsilon ε, gamma γ, zetaζ
Normal hemoglobins and adult percentages:
 Embryo
 Gower 2:
 Gower 1:
 Portland:
 Fetus
 F: α2γ2
 Adult
 A: α2β2
 A2: α2δ2
α2ε2
α2ε2
ζ2γ2
1-2%
95-97%
2-3%
Abnormal hemoglobins

Carboxyhemoglobin




Methemoglobin




Oxygen molecules bound to heme are replace by carbon monoxide.
Slightly increased levels of carboxyhemoglobin are present in heavy
smokers and as a result of environmental pollution.
Can revert to oxyhemoglobin.
Iron in the hemoglobin molecule is in the ferric (Fe3) state instead of the
ferrous (Fe2) state. Incapable of combining with oxygen.
Can occur as a result of strong oxidative drugs or to an enzyme
deficiency (more discussion to follow).
Can revert to oxyhemoglobin
Sulfhemoglobin



Hemoglobin molecule contains sulfur.
Caused by certain sulfur-containing drugs or chronic constipation.
Cannot revert to oxyhemoglobin and may cause death.