Session 10: Haemoglobin and Myoglobin Flashcards
Where does oxygen bind on the molecule?
Haem group
How many molecules of O2 can bind to the haem group in myoglobin and haemoglobin?
1
How many molecules of O2 can myoglobin bind?
1
How many molecules of O2 can haemoglobin bind?
4
How is the heam group bound to the protein?
Via a proximal histidine residue
Name 3 structural features of myoglobin.
- single chain polypeptide
- 153 aa
- 75% alpha helix
Where does the iron atom of the haem group sit in a deoxymyoglobin molecule? Why?
Just below the plane of the ring structure as the atom is too big to sit in the centre of the haem group
Why does the binding of oxygen cause the movement of the iron atom into the plane of the ring of a haem group?
Causes a conformational change
Describe the graph of myoglobins affinity for oxygen.
Hyperbolic
What is on the Y axis of an oxygen binding curve?
Fractional Saturation (percentage saturation of how many O2 molecules are bound to the protein)
What is on the X axis of an oxygen binding curve?
pO2 (partial pressure of oxygen)
Name the shape of a haemoglobin oxygen binding curve.
Sigmoidal
Name 2 structural features of haemoglobin.
- 2 polypeptides
- tetramer (4 subunits, two alpha, two beta)
Which state of deoxyhaemoglobin has the highest affinity for O2?
R state
What affect does the binding of O2 have on the state of deoxyhaemoglobin?
Stabilises the R state
Why is the oxygen binding curve for haemoglobin sigmoidal in shape?
Mixture of T and R state to allow either release of oxygen into tissues or acceptance of oxygen in the lungs respectively.
What is cooperative binding of oxygen?
When the binding of one oxygen molecule promotes the binding of subsequent molecules
TRUE OR FALSE: the binding of BPG powers the binding affinity of oxygen for haemoglobin.
TRUE
How many molecules of BPG bind per haemoglobin tetramer?
1
What’s the affect of an increase in BPG concentration?
Lowers the affinity of oxygen to haemoglobin hence releasing more oxygen into tissues
How does the binding of protons and carbon dioxide affect the affinity of haemoglobin for oxygen.
It lowers the affinity of haemoglobin for oxygen.
What is the Bohr effect?
When protons or carbon dioxide binds to haemoglobin, lowering the affinity for oxygen. It is important to ensure the delivery of O2 is coupled to demand.
Which binds more strongly to haemoglobin, carbon dioxide or oxygen?
Carbon dioxide
Does carbon dioxide contribute to cooperative binding of oxygen?
Yes
