STRUCTURE OF HAEMOGLOBIN

Haemoglobin is a quartenary structure protein that consists of 4 conjugated tertiary structure proteins.
Made up of two alpha polypeptide chains and two beta polypeptide chains.
Making up each subunit is a large, folded, polypeptide called globin. Between each two of the globin folds, there is a hydrophobic pocket that contains a heme group.
The Heme group consists of an atom of ferrous iron (Fe2+) and a surrounding porphyrin ring (four nitrogen-containing pyrrole molecules).
The iron atom can reversibly bind with one molecule of oxygen (O2).

Picture 1:The expired red blood cell cannot help the body anymore,so its destroyed by the macrophage in the spleen

The morphology of red blood cells will alter after 120 days, and they will eventually reach the spleen.
The stercobilin will be eliminated via the faeces.
The conjugated bilirubin will be transformed by intestinal bacteria into urobilin and stercobilin, which will be excreted in the urine.
The conjugated bilirubin, on the other hand, will go to the gall bladder and subsequently to the intestines.
The conjugated bilirubin will be transported to the kidney, where it will be eliminated in the urine, as previously stated.
Unconjugated bilirubin will be converted to conjugated bilirubin in the liver if there is sufficient glucoronic acid present.
Unconjugated bilirubin is delivered to the liver by albumin, a transport protein that is found in the blood.
Carbon dioxide will be expelled out of the body via the lungs.
When protoporphyrin is metabolised in the spleen, it results in carbon dioxide and unconjugated bilirubin (which is not water soluble).
Iron is transported out of the macrophage by transferrin into the bloodstream, where it is stored in different tissues or used to produce new red blood cells in the bone marrow.
Iron and protoporphyrin are formed as a result of haem degradation.
Globin is broken down into amino acids, which are then metabolised to produce new proteins.
Following the rupture of the red blood cell, the haemoglobin is absorbed by macrophages.

It is discharged as urine after reabsorption into a blood artery and reaching the kidney.