Transport of Oxygen by Hemoglobin

Red Blood Cells and Hemoglobin

• Function of Red Blood Cells:
  • Contain hemoglobin to transport oxygen in the blood.
• Structure of Hemoglobin:
  • Quaternary protein structure with more than one polypeptide chain.
  • Contains four polypeptide chains, each with a heme group containing iron where oxygen binds.

Types of Hemoglobin

• Hemoglobin is a group of proteins found in different organisms and tissues.
• Different types affect the ability to attract, load, and unload oxygen.
• Example: Myoglobin, which holds oxygen even at very low partial pressures.

Key Terms

• Affinity: Ability of hemoglobin to bind oxygen.
• Saturation: Max amount of oxygen hemoglobin can bind.
• Loading/Association: Binding of oxygen to hemoglobin.
• Unloading/Dissociation: Unbinding of oxygen from hemoglobin.

Oxyhemoglobin Dissociation Curve

• Shape: Sigmoid (S-shaped) curve.
• High Partial Pressure:
  • Hemoglobin is almost 100% saturated with oxygen.
  • High affinity, loading oxygen is easy.
• Low Partial Pressure:
  • Lower saturation, hemoglobin unloads oxygen.
  • Adaptation for respiring tissues with low oxygen.

Cooperative Binding

• First oxygen binds with difficulty but facilitates further oxygen binding by changing hemoglobin's shape.
• Results in a steep part of the curve, with saturation increasing rapidly as more oxygen binds.

The Bohr Effect

• Effect of CO2:
  • CO2 forms carbonic acid, makes blood acidic.
  • Shifts oxyhemoglobin curve to the right, reducing affinity for oxygen.
• Comparisons:
  • Less acidic (higher pH) means higher affinity and less oxygen unloading.
  • More acidic (lower pH) means lower affinity and more oxygen unloading.
• Advantage:
  • Ensures oxygen is unloaded at respiring tissues for aerobic respiration.

Hemoglobin Variations in Different Animals

• Fetal Hemoglobin (HbF):
  • Curve shifted left of adult hemoglobin, meaning higher affinity.
  • Advantageous for oxygen transfer from mother to fetus.
• Llamas:
  • Higher altitudes, lower oxygen pressure, curve shifted left for higher affinity.
• Doves:
  • Curve shifts right, decreasing affinity due to high metabolic need.
• Earthworms:
  • Living underground, curve shifted left to attract oxygen even at low pressures.

Summary

• Hemoglobins have different types and structures, adapted to specific environments.
• Oxygen binding and unloading are crucial for meeting metabolic demands.
• The Bohr Effect exemplifies how environmental conditions influence hemoglobin's function.

Additional Resources

• Practice questions and further learning available at Mrs. Truk's website.
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