Lecture 22 – Protein in action: Myoglobin and hemoglobin
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Questions and Answers

What is the primary function of hemoglobin in the blood?

  • To transport carbon dioxide
  • To carry oxygen (correct)
  • To facilitate glucose metabolism
  • To regulate blood pH
  • How much oxygen is typically carried in solution in blood?

  • 1%
  • 5% (correct)
  • 20%
  • 50%
  • At what partial pressure of oxygen (torr) does hemoglobin release oxygen most effectively?

  • 10 torr
  • 20 torr (correct)
  • 100 torr
  • 60 torr
  • What is the saturation of myoglobin in metabolizing tissue at 20 torr?

    <p>91%</p> Signup and view all the answers

    What type of binding does hemoglobin exhibit?

    <p>Cooperative binding</p> Signup and view all the answers

    What is the structure of myoglobin?

    <p>Monomer</p> Signup and view all the answers

    How many α-helices are present in the structure of myoglobin?

    <p>8</p> Signup and view all the answers

    What is the role of heme in myoglobin and hemoglobin?

    <p>It binds oxygen.</p> Signup and view all the answers

    What is the difference between the tetrameric structure of hemoglobin and myoglobin?

    <p>Hemoglobin has four binding sites; myoglobin has one.</p> Signup and view all the answers

    What are the two conformational states of hemoglobin?

    <p>T and R</p> Signup and view all the answers

    What effect does 2,3-bisphosphoglycerate (BPG) have on hemoglobin?

    <p>It decreases the affinity for oxygen.</p> Signup and view all the answers

    What does the term "sigmoidal binding curve" indicate?

    <p>Cooperative binding</p> Signup and view all the answers

    What is the primary sequence similarity between hemoglobin and myoglobin?

    <p>17% identical residues</p> Signup and view all the answers

    What is the Bohr effect?

    <p>Decreased oxygen affinity at lower pH</p> Signup and view all the answers

    What happens to the iron atom in heme when oxygen binds?

    <p>It is pulled into the plane of the heme.</p> Signup and view all the answers

    What type of protein is myoglobin classified as?

    <p>Transport protein</p> Signup and view all the answers

    What is the quaternary structure of hemoglobin described as?

    <p>Tetrameric</p> Signup and view all the answers

    How does the T state of hemoglobin differ from the R state?

    <p>T state has low affinity for oxygen; R state has high affinity.</p> Signup and view all the answers

    Which of the following stabilizes the T state of hemoglobin?

    <p>Low pH and CO2 binding</p> Signup and view all the answers

    What structural feature allows myoglobin to effectively bind oxygen?

    <p>The heme group</p> Signup and view all the answers

    What happens to hemoglobin's affinity for oxygen at high altitudes?

    <p>It increases due to lower oxygen levels.</p> Signup and view all the answers

    What is the significance of the proximal histidine in hemoglobin and myoglobin?

    <p>It coordinates the iron in heme.</p> Signup and view all the answers

    What is the role of distal histidine in heme?

    <p>It stabilizes oxygen binding.</p> Signup and view all the answers

    What is the effect of fetal hemoglobin (HbF) compared to adult hemoglobin (HbA)?

    <p>HbF has a higher affinity for oxygen.</p> Signup and view all the answers

    What is the primary function of myoglobin in muscle tissue?

    <p>To store oxygen</p> Signup and view all the answers

    What happens to the binding of oxygen to hemoglobin when the first oxygen molecule binds?

    <p>The affinity for oxygen in neighboring subunits increases.</p> Signup and view all the answers

    How does the presence of CO2 affect hemoglobin's oxygen affinity?

    <p>Decreases it</p> Signup and view all the answers

    Which model describes the binding of oxygen to hemoglobin as a series of sequential changes in conformation?

    <p>Sequential model</p> Signup and view all the answers

    What is the primary difference between the T state and R state in terms of oxygen binding?

    <p>R state has higher affinity for oxygen.</p> Signup and view all the answers

    Why is myoglobin not suitable for oxygen transport?

    <p>It binds oxygen too tightly.</p> Signup and view all the answers

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