Haemoglobin

• what is haemoglobin


  a globular protein made up 4 polypeptide chains - each chain contains a haem group (Fe2+ ion) - gives red pigment
• what is the reaction between oxygen and haemoglobin


  reversible reaction that forms oxyhemoglobin
• does haemoglobin have a high or low affinity for oxygen


  high- can carry 4 oxygen molecules
• why is th partial pressure of oxygen pO2


  a measure of oxygen concentration

  - the grater the concentration of dissolved O2 in cells the higher the partial pressure
• where does haemoglobin have the highest affinity for oxygen


  areas of high pO2 - lungs

  - oxygen loads onto haemoglobin
• where does haemoglobin have lowest affinity for oxygen


  areas of low pO2 - respiring tissues

  - oxygen unloads from haemoglobin

  - needed for respiration
• Explain an oxygen dissociation curve


  - where pO2 is high (lungs) haemoglobin has a high affinity for O2 - so will readily combine so has a high saturation

  -where pO2 is low (respiring tissues) haemoglobin has a low affinity for O2 - so releases oxygen so has a low saturation

  
• what is portion pressure of carbon dioxide pCO2


  measure of concentration of CO2 in a cell
• how does a high pCO2 affect haemoglobins affiinity for O2


  lowers its affinity

  -unloads oxygen

  - allows cells to get more O2 when exercising
• what is the Bohr effect


  When cells respire they produce carbon dioxide, which raises pCO2.

  This increases the rate of oxygen unloading (rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen.)

  The dissociation curve therefore shifts to the RIGHT.

  
• why is haemoglobin different in different organisms

  A = animal in depleted O2 env

  B = animal at high altitude- lower pO2

  C= human dissociation curve

  D = active animal with high respiratory rate in high O2 env

  EXPLANATION

  - organisms that live in env with low conc of O2 have hb with a higher affinity for O2 than human so curve is to the LEFT

  - organisms that are active and have high O2 demand have hb with lower affinity for O2 (unloads more readily) than human so curve is to RIGHT