METABOLISMO DE LA HEMOGLOBINA Y BILIRRUBINA || Morfofisiología

Overview of Hemoglobin and Bilirubin

Hemoglobin Function and Breakdown

• Hemoglobin is found in red blood cells and transports oxygen for approximately 120 days in circulation. After this, it becomes fragile and is destroyed by macrophages in the reticuloendothelial system.

• Macrophages break down hemoglobin into heme and globin. Globin decomposes into amino acids for protein synthesis, while heme is degraded by heme oxygenase into carbon monoxide, biliverdin, and ferrous iron.

Iron Transport and Erythropoiesis

• Ferrous iron binds to transferrin for transport to the red bone marrow where erythropoiesis occurs, forming new red blood cells released into circulation for another 120 days before destruction.

• Apart from the red bone marrow, iron also travels to the liver where hepatocytes store it by binding with ferritin. Biliverdin converts to unconjugated bilirubin which needs conjugation for transport.

Bilirubin Metabolism

• Unconjugated bilirubin binds with albumin for transport to the liver where it undergoes conjugation via UDP-glucuronyl transferase enzyme. This process involves glucuronic acid in 80% of cases.

• Conjugated bilirubin is expelled through the small intestine then converted by gut bacteria into urobilinogen (80%) or stercobilin giving color to feces. A portion returns to the liver as bilirubin diglucuronide while some exits as urobilin via urine coloring it.