Different types of haemoglobin

• Many organisms have a type of haemoglobin in their blood to transport oxygen, but it will have different affinities for oxygen depending on where the organism lives and their metabolic activities
• Foetus in the womb:

  • Higher affinity
  • Low oxygen in womb = Left

  
• Foetus in the womb:

  • Greater affinity to oxygen than adult haemoglobin
  • Oxygen binds to foetal haemoglobin more easily and is less likely to dissociate
  • Important as foetal haemoglobin needs to 'steal' oxygen away from the mother's haemoglobin when they pass in the placenta
  • If the foetal and maternal haemoglobin had the same affinity for oxygen, there would be no incentive for the oxygen to switch from the maternal blood to the foetal blood

  
• Animals living in low oxygen environments:

  • Their haemoglobin has a much higher affinity for oxygen
  • This is because when there isn't much oxygen available, the haemoglobin has to be able to load more oxygen at lower pO2 to make sure enough oxygen is absorbed

  
• Animals living in low oxygen environments:

  • Eg high altitudes where there is lower atmospheric pressure so low pO2
  • Higher affinity
  • Curve shifted to the left (Low O2 = Left)

  
• Small organisms with high SA:V or organism with high metabolic rate:

  • Lower affinity
  • Curve shifted to right (High Respiration = Right)

  
• Small organisms with high SA:V or organism with high metabolic rate:

  • Small mammals that have a higher SA:V than larger mammals will lose heat more quickly so they have a higher metabolic rate to help maintain their body temperature

  
• Small organisms with high SA:V or organism with high metabolic rate:

  • Higher metabolic rate = more respiration = greater oxygen demand
  • This means the organisms need haemoglobin with a lower affinity for oxygen as they need it to easily unload oxygen to meet their high oxygen demand and allow a faster respiration rate
• Why different haemoglobins have different affinities for oxygen:

  The shape of the molecule

  • Each species produces a haemoglobin with a slightly different amino acid sequence
  • Therefore a slightly different quaternary structure and hence different oxygen binding properties