Haemoglobin is a tetrameric protein which carries O2 and CO2.
Flavors of haemoglobin
There are different flavors of haemoglobin with different uses and properties. THe differences come what type of subunit combines with the alpha subunit. The flavours are HbA, HbA2, and HbF. each different type has different affinities for oxygen.
HbA
This is the most common type in adults, and is composed of 2 α subunits and 2 ß subunits.
Sickle cell disease
In sickle cell you can get a mutation in the ß subunit which causes different haemoglobin units to string together. this can alter the shape of the RBCs into a sickle shape, causing aggregation.
HbA2
This is a rarer combination of ∂ subunits and α subunits.
HbF
This is a combination of α subunits and γ subunits. this has a higher affinity for oxygen and is present in the fetal state, as the fetus needs to take oxygen from the mother. the higher binding affinity of the fetal isoform allows this
