• Haemoglobin is found in many different animal species.
• Different forms are also found within a species.
• The haem group has the same structure in all.
• The globin components differ.
• This affects the shape of the molecule.
• This affects:
  • Their ability to combine with oxygen.
  • The conditions in which they take up and release oxygen.
• Organisms who inhabit habitats with low oxygen concentration require haemoglobin that combines readily with oxygen:
  • They have an oxygen dissociation curves with a very steep gradient.
  • Eg lug worm
  • Eg llama
• Organisms with high metabolic rates require haemoglobin that releases oxygen readily:
  • Eg mice have a high SA:vol.
  • They lose heat easily.
  • They need a high metabolic rate.
  • Eg birds have a higher metabolic rate due to flight.
  • Their oxygen dissociation curve is further to the right.
  • They release oxygen more easily at the tissues.

• When it comes to IBDP Biology, the maternal haemoglobin releases its oxygen at the placenta .
• Oxygen concentration is relatively low.
• It diffuses across the placenta into the foetal blood.
• The foetal haemoglobin can pick up oxygen at these low concentrations.
• Curve is displaced to the left of adult curve.
• Foetal haemoglobin has higher affinity for oxygen than adult haemoglobin at any given partial pressure.
• After birth, the baby starts to make normal haemoglobin.

When it comes to IBDP Biology, myoglobin is

• Found in vertebrate muscles, particularly large mammals.
• Only one haem unit.
• Dissociation curve is displaced to the left.
• Myoglobin has greater affinity for oxygen than haemoglobin.
• Enable myoglobin to retain oxygen at low partial pressures.
• Acts as a store of oxygen.
• Oxygen released when at very low concentrations.
• I.E. during exercise.

This is the end of this topic

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