The role of haemoglobin

Question 1

What is the structure of haemoglobin?

Answer 1

• 4 globular polypepetide chains in a quaternary structure
• each polypeptide chain has a prosphetic group called the haem group
• each haem group contains the iron ion
• the iron binds to hydrogen

Question 2

How does reversible binding of oxygen work?

Answer 2

• oxygen binds to haemoglobin to form oxyhaemoglobin
• It can also dissociate to form deoxyhaemoglobin
• This is controlled by the relative concentration of oxygen and carbon dioxide at different locations of the body.

Question 3

What is oxygen affinity?

Answer 3

• Haemoglobin is more likely to associate with oxygen when partial pressure of oxygen is high and partial pressure of carbon dioxide is low
• oxygen has a greater affinity

Question 4

What happens if the partial pressure of oxygen is low?

Answer 4

• partial pressure of carbon dioxide is high
• It has a lower affinity for oxygen in these conditions

Question 5

What happens at lung/gas exchange?

Answer 5

• High partial pressure of oxygen
• low partial pressure of carbon dioxide
• low hydrogen concentration
• oxygen outcompetes hydrogen ions to bind to haemoglobin forming oxyhaemoglobin

Question 6

What happens at respiring tissues?

Answer 6

• low partial pressure of oxygen
• high partial pressure of carbon dioxide
• high hydrogen concentration
• hydrogen outcompetes ocygenions to bind to haemoglobin forming haemoglobin acid, oxygen is released