Proteins-- Haemoglobin Flashcards
What is the structure of Haemoglobin?
Two a-chains and two b-chains forming a tetradedral with Mr of 64,000
Why is the tertiary formation of HG important?
Transportation of H+, CO2 and O2,
What is O2 binding regulated by?
H+, CO2, 2,3-BPG as allosteric
What is the primary structure of Deoxyhaemoglobin?
141 AA a chains
146AA beta chains
Positive Co-operation
This is where change in shape of the first subunit makes bindig of the second substrate easiet.
Why is S1 o2 affinity important?
HG becomes a more effcienct transporter
What is HG p50 in HG?
26.6 WHILST mg 2.75
Why are HG regulators important?
Pure HB binds O2 too tightly for physiological needs
Bohr Effect
This is the property of vertebrate HG where pH changes affect HB-oxygen affinity t osuppport oading and unloading
How does lactic acid regulate Bohr Effect?
Formed on exercising muscles and venous blood acidificaiton occurs from CO2 dissolution and ioniziation increasing H+
What happens to ODC under acidic conditions?
Shifts to right and more O2 is released
Oxygen Dissociation Cruve
This is the expression of the relationship between the partial pressure of O2 and O2 saturation of HG
How does 2.3-BPG reglate?
Produeced by RBC by glycosist at 4-5mm concentrations
Why is 2,3-BPG glycosis generation useful?
Generated by activity usin O2 thus signalling more oxygen required
What is the physiological importance of 2,3-BPG?
In its absence, PO2 would not allow dissassociation of O2
How does temperature affect ODC?
Shifting it to the right thus increasing release of O2 in active muscle
Jpw dpes R amd T state conformationally differ?
Beta chain Fe distance from one another decrease from 3.99 to 3.34
What is T State contrained by?
Hydrophobic bonds and 8 electrostatic bonds involving the CTD AA of each subnit
What allows electrosttic bond formation in both chains?
Penultimate Tyr residue held within a pocket by H-bonding to a val
What is the T state stabilised by?
2,3-BPG binding with 8 elec trostatic bonds
What is the structure of the Haem in DHG?
F8 binds Fe above the porphyrin ring by 0.06nm
How does O2 affect haem group conformaiton?
Brings Fe 0.039nm closer to porphyrin plan, dragging His F8 to Helix F with EF corner and FG corner resulting in breakage of 8 electrostatic bonds
How does Tyr break the 8 electrostatic bonds?
Emergence of Tyr residues from the H-bonded pockets with valines breaking the bonds
How do the A-B dimer change rein conformation changes?
Rotate 15 degrees with respect to one another
