Hemoglobin Structure and Function
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Questions and Answers

What happens to the binding of oxygen to hemoglobin in a high pH environment?

  • Oxygen release from hemoglobin is facilitated.
  • No significant change in oxygen binding occurs.
  • Oxygen binds less tightly to hemoglobin.
  • Oxygen binds more tightly to hemoglobin. (correct)

    • What is the chemical equation that represents the Bohr Effect?

  • Hb(O2)nHx + O2 ⇌ Hb(O2)n+1 + xH+ (correct)
  • CO2 + H2O ⇌ H+ + HCO3-
  • Hb(O2)n + xH+ ⇌ Hb(O2)n+1 + xH
  • Hb(O2)n + CO2 ⇌ Hb(CO2)n + O2

    • Which of the following factors would lead to a decrease in hematocrit?

  • Increased blood viscosity.
  • Increased red blood cell size.
  • Decreased red blood cell size. (correct)
  • Increased red blood cell count.

    • What is the normal hematocrit range for newborn infants?

    <p>55-68 % (B)</p> Signup and view all the answers

    Which of the following is NOT a synonym for hematocrit?

    <p>Hemoglobin Level (A)</p> Signup and view all the answers

    What is the primary function of hemoglobin?

    <p>Carry O2 from the lungs to the tissues (D)</p> Signup and view all the answers

    Which of the following factors can cause a rightward shift in the oxygen dissociation curve of hemoglobin?

    <p>All of the above (D)</p> Signup and view all the answers

    What is the role of iron in hemoglobin?

    <p>Iron binds to the heme group, allowing it to transport oxygen (C)</p> Signup and view all the answers

    What is the effect of carbon monoxide (CO) on hemoglobin?

    <p>CO binds to hemoglobin, preventing it from carrying oxygen (D)</p> Signup and view all the answers

    What is the difference between hemoglobin A and fetal hemoglobin (Hb F)?

    <p>Hb F has a higher affinity for oxygen than Hb A (A)</p> Signup and view all the answers

    What is the role of 2,3-diphosphoglycerate (DPG) in hemoglobin?

    <p>DPG binds to hemoglobin, promoting the release of oxygen (B)</p> Signup and view all the answers

    During hemoglobin synthesis, where are the globin chains synthesized?

    <p>Ribosomes (C)</p> Signup and view all the answers

    Which of the following statements about methemoglobin is TRUE?

    <p>Methemoglobin is an abnormal form of hemoglobin that is unable to transport oxygen (A)</p> Signup and view all the answers

    Flashcards

    Normal Adult Hemoglobin (Hb A)

    Consists of four polypeptide chains: α2β2 and four heme groups.

    Heme Group

    Formed from protoporphyrin and iron (Fe2+) and gives hemoglobin its red color.

    Hemoglobin Structure

    Spherical, tetrameric protein with strong hydrophobic interactions and four heme groups.

    Oxygen Binding

    O2 binds to hemoglobin causing a conformational change to enhance oxygen release.

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    2,3-Diphosphoglycerate (DPG)

    Enhances oxygen release by stabilizing deoxyhemoglobin's quaternary structure.

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    Factors Affecting Dissociation Curve

    Curve shifts based on DPG, H+ ions, CO2 levels, and hemoglobin structure.

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    Right Shift of Curve

    Indicates easier O2 release; occurs with high DPG, H+, and CO2 concentrations.

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    Methemoglobinemia (Hb M)

    Abnormal hemoglobin formed when hemoglobin is oxidized, reducing O2 transport capability.

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    Bohr Effect

    The phenomenon where higher pH causes tighter oxygen binding to hemoglobin and lower pH promotes oxygen release.

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    Hematocrit

    The volume percentage of red blood cells in a blood sample after centrifugation.

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    Packed Cell Volume (PCV)

    Another term for hematocrit, referring to the volume of red blood cells.

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    Normal Hematocrit Ranges

    Normal values for hematocrit: Males 40-54%, Females 36-47%, Newborns 55-68%.

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    Microhematocrit Tube

    A capillary tube used to measure hematocrit, containing anticoagulant and marked with a red ring.

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    Study Notes

    Hemoglobin Structure

    • Normal adult hemoglobin A (Hb A) consists of four polypeptide chains (α2 β2) and four heme groups.
    • Normal adult blood also contains Hb F and Hb A2.
    • The table below details the structures and normal percentages of these hemoglobins.
    Hb Type Structure Normal (%)
    Hb A α₂β₂ 96-98
    Hb F α₂γ₂ 0.5-0.8
    Hb A₂ α₂δ₂ 1.5-3.2

    Hemoglobin Formation

    • Hemoglobin formation involves a series of steps:
      • 2 succinyl-CoA + 2 glycine → protoporphyrin IX
      • protoporphyrin IX + Fe²⁺ → heme
      • heme + polypeptide → hemoglobin chain (α or β)
      • 2 α chains + 2 β chains → hemoglobin A

    Hemoglobin Structure (Detail)

    • Hemoglobin consists of four globin chains (two α and two β), each containing a heme prosthetic group.
    • Heme is a porphyrin ring complex with an iron ion (Fe²⁺) at its center.
    • The iron ion binds oxygen.

    Hemoglobin Function

    • Carries oxygen from the lungs to the tissues.
    • Returns blood with carbon dioxide to the lungs.
    • When iron (Fe²⁺) is oxidized to iron(Fe³⁺), it forms methemoglobin, which is brown.
    • The dissociation of oxygen from hemoglobin depends on several factors:
      • 2,3-diphosphoglycerate (DPG)
      • H⁺ ions
      • CO₂
      • Hemoglobin structure

    Hemoglobin Synthesis

    • Hemoglobin synthesis occurs in the mitochondria.
    • Vitamin B₆ is a coenzyme for the reaction.
    • Iron (Fe) is supplied from circulating transferrin.
    • Globin chains are synthesized on ribosomes.
    • Protoporphyrin combines with ferrous (Fe²⁺) to form heme.
    • Four globin chains, each with its own heme, combine to form a hemoglobin molecule.

    Oxygen Dissociation Curves

    • Curve shifts right (O₂ is given up easily): High DPG, H⁺ or CO₂ concentrations and the presence of sickle hemoglobin (HbS).
    • Curve shifts left (O₂ is given up less readily): Fetal hemoglobin (HbF), inability to bind to 2,3-DPG, abnormal hemoglobins associated with polycythemia.

    Bohr Effect

    • Higher pH (low [H⁺]) promotes tighter O₂ binding to hemoglobin.
    • Lower pH (higher [H⁺]) permits easier release of O₂ from hemoglobin.

    Carbon Monoxide (CO)

    • Carbon monoxide (CO) disrupts the physiological function of hemoglobin.
    • Oxidized hemoglobin forms methemoglobin.

    Hematocrit

    • Hematocrit (HCT) is the volume percentage of red blood cells (RBCs) in a blood sample after centrifugation.
    • Also known as packed cell volume (PCV) or erythrocyte volume fraction (EVF).
    • Normal ranges:
      • Males: 40%-54%
      • Females: 36%-47%
      • Newborns: 55-68%
    • A decrease in RBC number or size lowers the hematocrit.
    • Hematocrit tests detect anemia or polycythemia.
    • Lower hematocrit results in less accurate hemoglobin and RBC counts.
    • Microhematocrit tubes are capillary tubes (75mm long, 1mm diameter) containing heparin (anticoagulant) and display red ring at the end.

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    Related Documents

    Hemoglobin (Structure, Function, and Synthesis) PDF

    Description

    Explore the intricate details of hemoglobin's structure, formation, and function in this quiz. Discover how different types of hemoglobin contribute to oxygen transport in the human body, including their unique structures and percentages. Test your knowledge on the biochemical processes involved in hemoglobin synthesis.

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