Adult Hb (Hb A) = 2 α and 2 β subunits
•HbA1 is the major form of Hb in adults and in children over 7 months.
•HbA2 (2 α, 2 δ) is a minor form of Hb in adults. It forms only 2 – 3% of
•a total Hb A.
Fetal Hb (Hb F) = 2 α and 2 γ subunits
- in fetus and newborn infants Hb F binds O2 at lower tension than Hb A → Hb F has a higher affinity to O2
After birth, Hb F is replaced by Hb A during the first few months of life.
Hb S – in β-globin chain Glu is replaced by Val
= an abnormal Hb typical for sickle cell anemia