37 out of 42
Heme is converted to bilirubin mainly in:
Ans. D Bone marrow
- When the RBCs have lived out their life span (average 120 days) and have become too fragile to exist longer in the circulation, their cell membrane ruptures and the released hemoglobin is phagocytized by tissue macrophages (also known as the reticuloendothelial system) throughout the body.
- Here, the hemoglobin is first split into globin and heme, and the heme ring is opened to give free iron that is transported in the blood by transferrin and a straight chain of four pyrrole nuclei that is the substrate from which bilirubin is formed
- The combination of monocytes, mobile macrophages, fixed tissue macrophages, and a few specialized endothelial cells in the bone marrow, spleen, and lymph nodes is also called the reticuloendothelial system.