haemoglobin

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  • Haemoglobin (Hb)
    • found in red blood cells
    • quaternary protein
      • 4 polypeptide chains
        • each coiled into a helix
        • contains heam group which contains Fe2+
    • transports O2
      • each each can carry 4 O2 molecules
      • O2 joins to Hb in RBC to form oxyhemoglobin
        • reversible reaction
        • Hb+4O2 ?  HbO3
    • Hb saturation depends on the particle pressure of O2 (pO2)
      • pO2 measures O2 concentration - the higher the pO2 the greater the concentration of dissolved O2
      • pCO2 is the CO2 concentrationin cells
        • Hb gives up O2 at higher pCO2
      • O2 loads into Hb to form HbO8 where there's a high pO2. Oxyheamaglobin unloads its O2 where there's a lower pO2
    • O2 enters capillaries at the alveoli. alveoli have high pO2 so O2 loads onto Hb to form HbO8
      • when cells respire pO2 lowers because RBCs deliver HbO8 to retiring tissues where it unloads O2
    • the dissociation curve for adult human haemoglobin
      • s-shape because when the Hb combines with the first O2 its shape alters in a way that makes it easier for others to join.
        • as Hb becomes more saturated its harder for O2 molecules to join
    • adaptation
      • organisms that live in low O2 concentrationenvironmentshave higher O2 affinity
        • curve shifts left
          • the dissociation curve for adult human haemoglobin
            • s-shape because when the Hb combines with the first O2 its shape alters in a way that makes it easier for others to join.
              • as Hb becomes more saturated its harder for O2 molecules to join

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