4. Haemoglobin I Flashcards
haemoglobin is tetrameric, what does tetrameric mean
4 subunits
what do each subunit contain
a haem group with its iron molecule
describe the structure of Hb polypeptide chains
4 chains: 2 alpha 2 beta
these subunits are packed in a tetrahedral array
describe contact between alpha and beta chains
alpha= little contact beta= no contact
what happens to Hb in urea
dissolves into two alpha- beta dimers
what 3 molecules regulate Hb-O2 binding
H+, CO2, 2,3-bisphosphate
what type of regulators are H+, co2 and 2-3 BP
allosteric - bind to spatially distinct sites
what is the p50 of haemoglobin
26.6 torr
what is cooperativity
The binding of O2 at one haem enhances the binding of O2 at other haems
what happens to Hb in the absence of regulators
haemoglobin binds oxygen too tightly for physiological needs
what is the job of regulators
each weaken the oxygen affinity to enable Hb to unload oxygen more easily
why is carbon dioxide the perfect regulator of Hb
at sites where oxygen is needed for respiration, CO2 is being produced
CO2 causes oxygen to dissociate by weakening the affinity, therefore oxygen is released to go back into the respiration cycle
describe the effect of H+ (Bohr effect)
- exercising muscles produce lactic acid- acidification of venous blood produces H+
- more H+ = more oxygen dissociates (weakens affinity)
- oxygen dissociation curve shifts
how is 2,3 BPG produced
in RBCs from glycolysis
where does 2,3 BPG bind
binds to deoxyhaemoglobin between the two beta subunits of Hb
