Mass transport

• what are the components of blood?

  • red blood cells
  • white blood cells
  • plasma
  • platelets
• what are the components of blood that are responsible for transporting oxygen?

  red blood cells
• haemoglobin is a protein. it has a quaternary structure which means that is has two or more polypeptide chains joined together
• how many polypeptide chains are joined together in haemoglobin?

  four
• how many molecules of oxygen can a single haemoglobin molecule carry?

  four
• in haemoglobin, each iron atom can bond to...

  one oxygen molecule
• when haemoglobin is bound to an oxygen, its called...

  an oxyhaemoglobin
• describe the structure of a haemoglobin

  the human haemoglobin is a protein with a quaternary structure because it contains four polypeptide chains. each polypeptide chain is bonded to a haem group containing an iron ion, which can bind to one oxygen molecule. this means that one molecule of haemoglobin can carry four molecules of oxygen. haemoglobin bound to oxygen is called oxyhaemoglobin.
• When a third oxygen molecule binds to haemoglobin, what happens?

  • the quaternary structure changes
  • more iron ions are uncovered
• what is positive cooperativity?

  when he binding or unbinding of one particle makes it easier for another to bind or unbind
• When the second oxygen molecule unbinds, positive cooperativity means that…

  it is easier for another oxygen molecule to unbind
• The process of oxygen binding to haemoglobin is known as...

  oxygen association
• The process of oxygen unbinding from haemoglobin is known as...

  oxygen dissociation
• Positive cooperativity speeds up the transfer of oxygen from…

  • red blood cells into aerobically respiring tissue
  • air in the alveoli to red blood cells
• what is oxygen association and dissociation influenced by?

  the partial pressure of oxygen
• when the partial pressure of oxygen is high...

  association takes place
• when the partial pressure of oxygen is low...

  dissociation takes place
• why does oxygen association occur in the lungs?

  because the partial pressure of oxygen is higher in the lungs than in the blood
• why does oxygen dissociation occur in respiring tissues ?

  • the partial pressure of oxygen is lower in the tissues than in the blood
  • oxygen diffuses down its pressure gradient
• order of the partial pressure of oxygen increasing:

  • respiring tissues
  • blood
  • lungs
• what is pressure usually measured in?

  pascals (Pa)
• what is partial pressure of oxygen usually measured in ?

  • kilopascals (kPa) 1 kPa=1000 Pa
  • millimetres of mercury (mm Hg)
• As the partial pressure of oxygen increases, the percentage saturation of haemoglobin with oxygen…

  increases
• The percentage saturation of haemoglobin with oxygen is a measure of how many iron ions in the haemoglobin molecules…

  are bound to oxygen
• in the oxyhaemoglobin dissociation curve, what does the steep change in the gradient indicate?

  positive cooperativity
• Suggest why the percentage saturation of haemoglobin with oxygen does not reach 100% in the lungs.

  • the probability of a collision between an unbound iron atom and an oxygen molecule is low
  • most iron atoms are already bound to an oxygen molecule
• why does the gradient of the curve in the oxyhaemoglobin dissociation curves start to increase at the start?

  The increase in gradient is due to positive cooperativity. When an oxygen molecule binds to haemoglobin, it makes it easier for another oxygen molecule to bind. This causes the percentage saturation of haemoglobin with oxygen to increase rapidly.
• where does the line shift if there is a lower concentration of carbon dioxide in the blood in the oxyhaemoglobin dissociation curve?

  to the left
• where does the line shift if there is a higher concentration of carbon dioxide in the blood in the oxyhaemoglobin dissociation curve?


  to the right
• Blood with a lower concentration of carbon dioxide has…

  a higher partial percentage saturation of haemoglobin with oxygen
• At higher carbon dioxide concentrations, oxygen…

  • associates less readily with haemoglobin
  • dissociates more readily with haemoglobin
• At lower carbon dioxide concentrations, oxygen…

  • associates more readily with haemoglobin
  • dissociates less readily with haemoglobin
• At higher carbon dioxide concentrations, oxygen…

  • associates less readily with haemoglobin
  • dissociates more readily with haemoglobin
  • much better at unbinding with oxygen molecules
• At lower carbon dioxide concentrations, oxygen…

  • associates more readily with haemoglobin
  • dissociates less readily with haemoglobin
  • much better at binding with oxygen molecules
• Haemoglobin molecules are proteins, so changes in acidity can change the…

  shape of the molecule
• Carbon dioxide reacts with water in our blood to form…

  H+ ions
• When the concentration of carbon dioxide in the blood increases…

  • H+ concentration increases
  • pH decreases
• As the blood’s pH increases…

  • the shape of the haemoglobin changes
  • its easier for oxygen to associate
• how is the Bohr effect beneficial for exercise?

  respiring muscles release carbon dioxide which decrease the pH of the blood near the tissue. this causes haemoglobin to change shape, allowing oxygen to associate more readily. as a result cells are provided with more oxygen for aerobic respiration.
• what gas is released by aerobically respiring muscle cells

  carbon dioxide