Haemoglobin Flashcards
How is haemoglobin a tetramer
Made up of 4 monomers 2-alpha and 2-beta
What is the purpose of myosin
Monomeric haem protein found in muscle tissue.
Facilitates oxygen transport in rapidly respiring muscle.
Receives oxygen from hb.
What is the shape of the oxygen saturation curve does hb have?
Sigmoidal (s-shaped)
What is cooperative binding?
If its affinity for its ligand changes with the amount of ligand already bound.
What are the two states of hb
T-state (deoxyhaemoglobin) and R-state (oxyhaemoglobin)
Why does Hbf have a higher affinity for oxygen the Hba
It takes oxygen from Hba so it has to have a higher affinity.
What is the Bohr effect?
A reduction in the affinity for oxygen of haemoglobin when pH decreases (increases in CO2, carbonic acid formed decreases pH)
What is 2,3-BPG and what does it do
2,3-bisphosphoglycerate, lowers affinity for oxygen of Hb by stabilising the Hb T state
What is different between sickle cell hb and normal hb
In the b subunit of sickle cell, at the 6th position (near outside, on surface of protein) a glutamic acid (glutamate) is replaced with a valine. Valine is non polar and so while on surface of protein it creates a hydrophobic region that will polymerise with other hb molecules.
How do the subunits within hb change during foetal development/after birth
Gamma subunits replaced by B-subunits
How is haem involved in hb structure?
Stabilsed between helices E (distal histidine) and F (proximal histidine).
The distal histidine in the E helix stabilises the O2 bound form and helps to destabilise the CO bound form
How does oxygen binding cause a conformational change in hb structure?
It induces the movement of the Fe ion towards the haem plane
Then induced movement of the F helix
This helps facilitate the allosteric transition of t-state to r-state
How does hb carry CO2
It forms carbaminohaemoglobin when CO2 reacts with the Hb n-terminus (produces carbamino terminal residues)
How is CO2 transported in the blood
Mostly as HCO3-, CO2 can react with water to form carbonic acid (which dissociates) catalysed by carbonic anhydrase; this reaches the lungs and the same enzyme catalyses the reverse reaction.
Also CO2 can react with the N-terminus of hb to produce carbamino terminal residues/carbaminohaemoglobin
How does Hb carry H+ ions
As a buffer does
