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MLAB 1315- Hematology Fall 2007 Keri Brophy-Martinez

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Title: MLAB 1315- Hematology Fall 2007 Keri Brophy-Martinez


1
MLAB 1315- HematologyFall 2007Keri
Brophy-Martinez
  • Unit 6 Hemoglobin

2
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

3
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

4
Structure
  • Structure
  • Globin a tetramer of two pairs of unlike globin
    polypeptide chains
  • 2 alpha (a) chains
  • 2 beta (ß) chains
  • 4 heme groups, each of which contains a
    protoporphyrin ring plus Fe . Iron can only
    bind oxygen in the ferrous (Fe) state.

5
Structure
  • Fe

  • Heme Globin HEMOGLOBIN
  • Protoporphyrin

6
Structure
7
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.

8
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 RBCs, they act
    more efficiently to deliver O2 to target

9
Oxygen Dissociation Curve
  • Left shift
  • Hgb has more attraction for O2
  • Hgb less willing to release O2 to tissue
  • Examples presence of abnormal Hgbs, alkalosis

10
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.

11
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

12
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

13
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 a, beta ß, delta d, epsilon e, gamma ?,
    zeta?

14
Normal hemoglobins and adult percentages
  • Embryo
  • Gower 2 a2e2
  • Gower 1 a2e2
  • Portland ?2?2
  • Fetus
  • F a2?2 1-2
  • Adult
  • A a2ß2 95-97
  • A2 a2d2 2-3

15
Abnormal hemoglobins
  • Carboxyhemoglobin
  • 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.
  • Methemoglobin
  • 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.
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