haemoglobin

• how many oxygen molecules can 1 haemoglobin molecule bind to

  4
• what is formed when oxygen binds to haemoglobin e.g. in the lungs

  oxyhaemoglobin
• what type of reaction is oxygen + haemoglobin --> oxyhaemoglobin

  reversible - oxygen can dissociate from it near body cells
• what is partial pressure of oxygen

  Measure of oxygen concentration
• what does haemoglobin's affinity for oxygen depend on

  the partial pressure of oxygen
• what causes oxygen to a) unload and b) load

  oxygen load onto haemoglobin where there's a high pO2

  oxyhaemoglobin unloads it's oxygen where there's a low pO2
• where is partial pressure of oxygen high

  alveoli so oxygen loads onto haemoglobin
• Where is the partial pressure of oxygen lowest?

  respiring cells - as they respire, they use up oxygen so lower the partial pressure so oxygen unloads
• why is the oxygen dissociation curve s shaped

  When haemoglobin combines with the 1st O2 molecule, its shape alters, making it easier for other O2 molecules to join too, but as Hb becomes more saturated, it's harder for the other molecules to join too as they are less likely to collide
• what is it called where the shape of Hb changes when O2 molecules bind to it making it easier for others to bind

  positive cooperativity
• how does a high partial pressure of CO2 affect haemoglobin's affinity for oxygen

  it decreases haemoglobin's affinity for oxygen
• what is the Bohr effect

  when CO2 levels increase, the dissociation curve shifts to the right, showing that more oxygen is released from the blood
• what is an advantage of the bohr effect

  respiring cells release CO2 by aerobic respiration, so haemoglobin's affinity for oxygen decreases so it unloads oxygen to be used for respiration
• how does the affinity of fetal haemoglobin compare to adult

  fetal haemoglobin have a higher affinity for oxygen
• why does the fetal haemoglobin have to be higher than the adult haemoglobin

  by the time the mother's blood reaches the placenta, its oxygen saturation has decreased as it has been used up by the mother
• what are the 3 ways that carbon dioxide is transported

  dissolved in the blood plasma

  combined with amino groups in haemoglobin to form carboaminohaemoglobin

  most is converted into hydrogen carbonate ions in the cytoplasm of erythrocytes
• list the steps to make hydrogen carbonate ions

  1) CO2 reacts with water in the cytoplasm of erythrocytes to form carbonic acid, catalysed by the enzyme carbonic anhydrase

  2) carbonic acid dissociates into H+ ions and HCO3- ions

  3) this increase in H+ ion concentration causes oxyhaemoglobin to unload its oxygen so that haemoglobin can bind with H+ ions to form haemoglobinic acid and stops the H+ ions from lowering the pH
• describe the chloride shift

  the HCO3- ions diffuse out of the erythrocyte and are transported by the blood plasma, to balance the charge, the Cl- ions diffuse into the erythrocyte
• how is carbon dioxide breathed out

  when the blood reaches the lungs, the low pCO2 causes some of the HCO3- and H+ ions to recombine into CO2 which diffuses out of the alveoli