Myoglobin and Oxygen Dissociation Curves

Myoglobin

• Function: Protein in muscles with a high affinity for oxygen; stores oxygen in muscle tissue.
• Oxygen Binding: Strong binding due to high affinity, making it a storage protein.
• Oxygen Dissociation Curve:
  • The curve is almost vertical.
  • Fully saturated at approximately 8 kilopascals of oxygen.
• Purpose: Supplies oxygen to muscles during extreme physical activity (e.g., biking, running).
• Extreme Activity Scenario:
  • Circulatory system can't deliver enough oxygen.
  • Muscles may start anaerobic respiration, producing lactic acid and CO2.
  • Lactic acid and CO2 lower myoglobin's affinity for oxygen, causing oxygen dissociation to provide more oxygen for aerobic respiration.

Surface Area to Volume Ratio and Oxygen Dissociation Curves

• Example Animals: Mouse and Elephant.
• Dissociation Curves:
  • Mouse curve is to the right of the elephant's.
  • Rightward curve indicates lower affinity for oxygen.
  • Leftward curve indicates higher affinity for oxygen.

Factors Affecting Oxygen Affinity

• Surface Area to Volume Ratio:
  • Mouse has a high surface area to volume ratio; elephant has a low one.
• Heat Loss and Respiration:
  • Mouse loses more heat due to higher surface area to volume ratio and needs more aerobic respiration to replace heat.
  • Requires hemoglobin with lower affinity for oxygen to dissociate easily and meet high respiration demands.
  • Elephant loses less heat and thus, does not need as much aerobic respiration and doesn't need lower affinity hemoglobin.

Key Concepts

• Animals with different surface area to volume ratios have hemoglobins with different oxygen affinities.
• Smaller animals lose more heat and thus, require hemoglobin that releases oxygen more readily to support higher rates of respiration.