Haemoglobin is a complex, iron-containing protein in red blood cells (RBCs) that binds and transports oxygen from the lungs to tissues throughout the body.
Hemoglobin consists of four protein subunits, each containing a heme group with an iron atom at its center.
Steps in Formation of haemoglobin:
1. Synthesis of Globin Chains:
Hemoglobin in adults (HbA) comprises two alpha (α) chains and two beta (β) chains.
The α-globin chains are encoded by genes on chromosome 16, while β-globin chains are encoded on chromosome 11.
These chains are synthesized in the ribosomes of developing red blood cells in the bone marrow.
2. Synthesis of Heme:
Heme is an organic molecule essential for oxygen binding, with an iron atom at its center.
Heme synthesis occurs in the mitochondria and cytoplasm of immature red blood cells.
The process begins with the condensation of succinyl-CoA and glycine to form δ-aminolevulinic acid (ALA) in the mitochondria, followed by a series of transformations in the cytoplasm, leading to the formation of the porphyrin ring and the insertion of an iron atom to complete the heme molecule.
3. Assembly of Hemoglobin:
The synthesized globin chains bind to the heme groups, forming hemoglobin subunits.
Two α-globin subunits associate with two β-globin subunits, creating the functional hemoglobin molecule (α2β2).
4. Maturation of Red Blood Cells:
As red blood cells mature in the bone marrow, they accumulate hemoglobin, lose their nucleus and organelles, and adopt a biconcave shape.
Mature red blood cells, filled with hemoglobin, are then released into the bloodstream to transport oxygen to tissues and organs