7.2 - O2 transport via haemoglobin

• How does haemoglobin change its affinity ?

  Conformational change
• What‘s positive cooperativity ?

  Binding of the first O2 molecule on haemoglobin changes quaternary shape and induces/makes it easier for the other molecules to bind
• What does the oxygen dissociation curve show ?

  Relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen
• Explain the shape of the oxygen dissociation curve ?

  • At low pO2, Hb saturation is low as the Hb shape is closed so O2 struggles to bind, association is low
  • after 1 molecule has associated, positive cooperativity occurs, smaller pO2 increases are needed to increase saturation, graph has steep increase
  • after 3rd O2 binds there’s less probability of a 4th molecule binding, association is lower, graph plateaus
• The further left the curve is, the …… the affinity of Hb for O2 ?


  Greater
• The further right the curve is, the ….. the affinity of Hb for O2 ?


  Lower
• What’s the Bohr effect ?

  Greater the CO2 conc, the more readily O2 dissociates with Hb. At any pO2, affinity of Hb for O2 is lower
• What does a decrease in pCO2 do to the curve and why ?

  Shifts it to the left, affinity for O2 is high and pO2 increases in lungs, O2 readily associates with O2
• What does an increase in pCO2 do to the curve ? (In respiring tissues)

  Affinity of Hb for O2 is low and there’s a low pO2 so curve shifts right as oxygen readily dissociates
• Explain how high pCO2 cause a conformational change in Hb ?

  High CO2/lactate conc, acidic so an increase in H+ ions in blood, change in pH alters Hb tertiary structure,conformational change favours dissociation and lowers O2 affinity, respiring issues receive more O2
• How does fetal Hb differ from adult Hb ?

  Fetal Hb has a higher affinity for oxygen than adult Hb