haemoglobin

• what are red blood cells specialised to carry?

  to carry oxygen.
• what do red blood cells contain a lot of?

  haemoglobin.
• what is haemoglobin?


  a large protein, made of 4 subunits. Got a quaternary structure. Each of the 4 polypeptide chains contains a haem group containing a Fe2+ ion which is what binds to the oxygen.
• what is oxygen binding often called?

  loading.
• what's the reaction like for oxygen loading to haemoglobin?

  reversible. oxygen + haemoglobin --> oxyhaemoglobin.
• what is concentration of oxygen like in the lungs?

  high conc of oxygen.
• what is concentration of oxygen like in the tissues?

  low conc of oxygen
• what happens with oxygen at the lungs?

  in the lungs at the alveoli oxygen enters the capillaries and loads onto haemoblonin as it has a high affinity for oxygen cause high conc of oxygen.
• what is an affinity for oxygen?

  the tendency a molecule has to bind to oxygen.
• what is the concentration of oxygen like in the tissues?

  low as it has been used up for respiration
• what is haemoglobin's affinity for oxygen like at the tissues?

  low because low conc of oxygen.
• at the lungs oxygen..


  ..readily loads.
• at the tissues oxygen..

  ..readily unloads
• what does the partial pressure of oxygen mean?

  the concentration of oxygen.
• on the oxyhaemoglobin dissociation curve, what does the point where the partial pressure of oxygen is high show?

  shows what the % saturation of haemoglobin is like at the lungs.
• on the oxyhaemoglobin dissociation curve, what does the point where the partial pressure of oxygen is low show?

  the % saturation of haemoglobin at the tissues.
• look at this and learn

  
• why does the lungs have this position on the curve?

  haemoglobin is saturated with oxygen bc haemoglobin has a high affinity for oxygen so it loads.
• why do the tissues have this position on the curve?

  haemoglobin is less saturated with oxygen bc haemoglobin has a low affinity for oxygen so it unloads.
• At low partial pressure of oxygen


  As we increase the oxygen, the % saturation of haemoglobin doesn't increase much
• At higher partial pressure of oxygen


  The % saturation of haemoglobin increases quickly for a small increase in oxygen
• Cooperative nature of oxygen binding

  After the 1st oxygen molecule binds, the shape of the haemoglobin changes so it's easier for the 2nd and 3rd oxygen molecules to bind, so it has a higher affinity for oxygen
• As oxygen further increases


  The rate of increase in % saturation increases
• After haemoglobin becomes more saturated


  It gets harder for further molecules to bind, which is why it plateaus
• Graph shape


  • S-shaped
• what causes the curve to shift to the right?

  carbon dioxide.
• what is the Bohr Effect?

  as we increase the carbon dioxide in our blood (eg: during exercise) we lower the pH of the blood reducing the affinity of haemoglobin for oxygen bc haemoglobin changes shape making it harder for molecules to bind. This is beneficial as it increases the amount of oxygen being unloaded from haemoglobin at the tissues and the oxygen is used for respiration.
• in an exam, if you are asked to use the graph to explain there Bohr Effect. What do you do?

  use the graph to find the conc of oxygen at the tissues and the corresponding % saturation of haemoglobin at each of the curves. This shows the particular partial pressure of oxygen the % saturation of haemoglobin will be lower.
• what organisms is haemoglobin found in?


  many different organisms.
• how is haemoglobin different in different organisms? why?

  organisms can adapt to their environment by having different types of haemoglobin with different transport proteins. The haemoglobin structure can vary as its a protein made of amino acids and when changing the amino acids the haemoglobin can have a different structure bc its primary structure changes so it folds differently.
• what does it mean when the curve has shifted to the left?

  haemoglobin has a higher affinity for oxygen and so loads more readily in the lungs at a lower oxygen concentration. This is the main advantage!! Useful for organisms in low oxygen environments as they can load more oxygen in the lungs. eg: fetal haemoglobin, has a higher affinity for oxygen than adult haemoglobin which is important as by the time mothers blood reached placenta its oxygen saturation has decreases as its used by mothers body so fetal has to be better at absorbing oxygen so it can still get oxygen.
• what does it mean when the curve has shifted to the right?

  haemoglobin has a lower affinity for oxygen. beneficial for tissues, at the same partial pressure of oxygen in tissue the haemoglobin has lower saturation of oxygen so more has been unloaded to tissues. Important for organisms that need more oxygen in their tissues. eg: high metabolic rate.