Varieties of Hemoglobin:-
1). Adults Hb (HbA)
2). Fetal Hb
3). Hemoglobin S (Sickle)
1). Adults Hemoglobin:- It is of two types.
a). HbA (α2β2)
b). HbA2 (α2γ2)
a). HbA:- Predominantly seen two α-Chains and 2β-Chains in this HB.
b). HbA2:- α2γ2 Here β-chain are replaced by γ-chain. The γ-chain also contains 146 amino acids but 10 individual amino acids differ from those in β-chain approx 2.5% of the total HbA2 in normal adults.
2). Fetal Hb:-
a). (α2γ2) it structures same as HbA except that the β-chain is replaced by γ-chain. γ-chain also contains 146 amino acid but have 37 amino acid that differs from those in the β-chain.
b). HbF has a greater affinity for oxygen.
c). Its life span is less about 80 days as compared to that of HbA.
3). Hemoglobin Sickle(HbS):- Here in each β-chains of HBA at position 6 on glutamic acid replace by valine. Therefore HbS reduced as [Example as in low oxygen tension at tissue level]. It becomes much less soluble than hbA. Hb precipitate into crystals within the RBCs it Causes:-
a). It damages the cell membrane producing an increased Fragility of RBCs.
b). Crystals elongate and RBCs become sickle shape(hook shape). Which decreases the blood flow to the tissue, RBCs become more. Fragile-producing severe(critical) anemia is called sickle cell anemia. Finally patient dies in a few days due to severe anemia and secondary infection.
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