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MLAB 1415- Hematology Keri Brophy-Martinez

MLAB 1415- Hematology Keri Brophy-Martinez. Chapter 6: Hemoglobin. Hemoglobin. What is it? Iron- bearing protein which is the main component of the RBC Gives the red cell its color Synthesis Majority synthesized at the polychromatophilic normoblast stage Regulation

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MLAB 1415- Hematology Keri Brophy-Martinez

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  1. MLAB 1415- HematologyKeri Brophy-Martinez Chapter 6: Hemoglobin

  2. Hemoglobin • What is it? • Iron- bearing protein which is the main component of the RBC • Gives the red cell its color • Synthesis • Majority synthesized at the polychromatophilic normoblast stage • Regulation • Stimulated by tissue hypoxia • Hypoxia causes the kidneys to increase production of EPO, which increases RBC and hemoglobin production • 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)

  3. Hemoglobin Reference Ranges • Adults • Male 14-17.4 g/dL • Female12-16.0 g/dL • 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 age ranges

  4. Structure • 4 polypeptide Subunits • Heme group • Porphyrin ring • Ferrous iron • Globin chain • 2 Alpha Chains • 2 Beta chains

  5. Hemoglobin Synthesis • Synthesis • Occurs in the mitochondria 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

  6. Heme Synthesis • Chain of Events • Iron delivery & supply • Iron is delivered to the reticulocyte by transferrin • Synthesis of protoporphyrins • Occurs in the mitochondria of RBC precursors • Mediated by EPO and vitamin B6 • Protoporphyrin + iron = heme

  7. Globin Synthesis • Chain of Events • The rate of globin synthesis is proportional to the rate of porphyrin synthesis. • 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. • Chain designations are as follows • Alpha α, beta β, delta δ, epsilon ε, gamma γ, zetaζ

  8. Normal hemoglobins

  9. Hemoglobin Synthesis

  10. Oxygen transport • The amount of O2 bound to hemoglobin and released to tissues depends on PO2 and PCO2, but also the affinity of hemoglobin for O2. • Oxyhemoglobin: hemoglobin with oxygen • Deoxyhemoglobin: hemoglobin without oxygen • Oxygen affinity is the ease with which hemoglobin binds and releases oxygen.

  11. Oxygen Affinity • Determines the proportion of O2 released to the tissues or loaded onto the cell at a given oxygen pressure. • Increases in oxygen affinity means hemoglobin has an increased affinity for O2, so it binds more. However, it does not want to give it up. • Decreases in oxygen affinity, cause O2 to be released.

  12. Bohr Effect • Alterations in blood pH, shifts oxygen dissociation curve • In acidic pH, the curve shifts to the right • Results in an enhanced capacity to release O2 where it is needed

  13. 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

  14. 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

  15. Carbon Dioxide Transport • Three mechanisms of transport • Dissolution in the plasma • Formation of bicarbonic acid • Binding to carbaminohemoglobin

  16. Nonfunctional hemoglobins • What do they do? • Hypoxia • Inadequate amount of O2 in the blood • Cyanosis • Presence of > 5 g/dl deoxyhemoglobin in blood • Patient appears blue

  17. Nonfunctional hemoglobins • Carboxyhemoglobin • Oxygen molecules bound to heme are replaced 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.

  18. References • McKenzie, S. B. (2010). Clinical Laboratory Hematology (2nd ed.). Upper Saddle River, NJ: Pearson Education, Inc..

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