Page 290 - Biochemistry PharmD General

HbM or Methemoglobin

• The defect lies both in α and β chains. This is due to
replacement of histidine residue in 58th position in α
chain and 63rd position in β chain.

• Due to this replacement, the iron (Fe) present in the

ferrous state is oxidized to ferric state. This ferric

iron cannot bind oxygen. Therefore the oxygen carrying

capacity is disrupted leading to anemia and hypoxia (low

O2 to tissues).

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. 289