Haemoglobin Flashcards
What protein is involved in the transport of oxygen from the lungs to the tissues?
Haemoglobin
Describe the structure of haemoglobin?
- Consists of 4 globin chains, HbA has 2 alpha chains and 2 Beta chains
- Each globin chain contains a haem group
- Each Haem group is made up from a central ferrous iron atom (fe2+) surrounded by a porphyrin ring
What four chains are HbA molecules made up from?
Two alpha chains and 2 beta chains
What two chain type is fetal haemoglobin made from?
Two alpha chains and two gamma chains
What is meant by the positive cooperative binding which oxygen displays?
This means that it becomes easier for oxygen to bind as more oxygen binds to it - hence resulting in the sigmoidal curve which arises when oxygen dissociation is plotted
How is the oxygen affinity different in fetal haemoglobin compared with adult haemglobin?
The oxygen affinity is higher
How does HbF have a higher oxygen affinity than HbA?
A single AA substitution results in reduced affinity for 2,3-DPG and therefore a higher oxygen affinity
Why is it essential that fetal haemaglobin has a high affinity for oxygen?
This means at very low concentrations of oxygen, which the placenta has, HbF can still readily bind the oxygen which the HbA is offloading
Why can myoglobin not display positive cooperativity?
It only has one oxygen binding site
What is the p50 value for myoglobin and haemaglobin respectively?
Myoglobin = 2
Hb = 26
Where is myoglobin found?
Predominantly in the muscle cells
Why is myoglobin useful?
It is a store of oxygen, which is mainly found in the muscles, and has a high affinity fr oxygen - it only releases the oxygen it is storing when the oxygen concentration is very low
A right shift in the oxygen dissociation curve is associated with what change?
A decrease in the oxygen affinity
A left shift in the oxygen dissociation curve is associated with what change?
AN increase in the oxygen affinity
What factors could cause an increase in the oxygen affinity (Left shirt)?
Decreased CO2, Decreased 2,3-DPG, Decreased H+
What factors could cause a decrease in the oxygen affinity (right shift)?
Increased CO2, Increased H+, Increased 2,3-DPG and increased temperature
Describe how a left shift in the oxygen dissociation curve results in an increase in the affinity for oxygen?
When the curve shifts left, at the same partial pressure of oxygen, the saturation of the haemoglobin molecules is higher. This is because as the affinity is higher, the Hb is less willing to release the oxygen molecules and therefore the Hb is more saturated