Human hemoglobin has
Four polypeptide chains belong to α-type
Four polypeptide chains with 3 of them α-type and one β-type.
Four polypeptide chains with 2 of them α-type and remaining two β-type
Two polypeptide chains with one of them α-type and one β-type.
Human hemoglobin is a tetrameric protein having two α-type and two β-type polypeptide chains.