Page 31 - General Biochemistry

• Due to this replacement there is a sticky patch on HbS which appears on the
oxy HbS.

Types of Hemoglobin

There are three types of hemoglobin’s that are normally found in human beings,
they are

1. HbA
Found in normal adult human beings – contains 2α and 2β chains.
2. HbA2
Found in some human beings and is considered normal — contains 2α and 2δ

chains (α2δ2).
3. HbF
Foetal hemoglobin — found in growing foetus — contains 2α and 2ƴ chains.

Thalassemia’s
• The defect in thalassemia’s is the decreased rate of synthesis of one of the

polypeptide chains of the globin molecule.
• One of the chains is synthesized in less amounts than the other due to the

defect in DNA.
• There are two types of thalassemia, α-thalassemia and β-thalassemia.

β-thalassemia

• β-thalassemia occurs due to the decreased synthesis rate of beta-chain of
globin.

• Due to the deficiency of beta-chain, the a-chains either combine among
themselves forming a-4-globin or it can combine with Y or δ chains, thereby
forming more of HbA2 and HbF.

• This results in the impairment of the transport of O2 by Hb resulting in
hypoxia.

• The life span of such RBC is greatly reduced.
• The symptoms include anemia, growth retardation, wasting and fever.

α-thalassemia
• α-thalassemia occurs due to the decreased rate of synthesis of α-chain of

globin.
• This is rarely seen due to the presence of two pairs of genes for a chain in

the Hb gene.
Glucose-6-Phosphate Dehydrogenase Deficiency

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