Structure of haemoglobin
Globular
water soluble
Consisted of four polypeptide chains Each carrying a haem group - (quaternary structure)
Each haem group contains and iron ion giving blood the red colour
Role of haemoglobin
Present in red blood cells - oxygen molecules bind to the haem group and are carried around the body to where they are needed in respiring tissues
Haemoglobin has a high affinity for oxygen
Takes up oxygen more easily and releases it less easily
How does partial pressure of oxygen affect the binding of oxygen to haemoglobin
As pO2 increases haemoglobin affinity for oxygen increases so oxygen binds tightly to haemoglobin. When pO2 is low oxygen is released from haemoglobin
Bohr effect
When the partial pressure of carbon dioxide (pCO2) increases the conditions become more acidic causing haemoglobin to change shape, the affinity of haemoglobin for oxygen then decreases and oxygen is released.
How does the saturation of haemoglobin with oxygen affect the oxygen haemoglobin binding
Hard for the first molecule to bind
Haemoglobin changes shape too make it easier for the other molecules to bind
Becomes slightly harder for the fourth oxygen molecule to as there is a lower chance of finding the binding site
Explain why oxygen binds to haemoglobin in the lungs
pO2 is high
Low concentration of co2 in lungs so affinity is high
Positive cooperativity
What does a oxyhaemoglobin dissociation curve show
saturation of haemoglobin with oxygen plotted against the partial pressure of oxygen
Curves further to the left show that haemoglobin has a higher affinity for oxygen
How does carbon dioxide affect them position of an oxyhaemoglobin dissociation curve
Shifts to the right because haemoglobin’s affinity for oxygen has decreased