edson sospeter
Dec 26, 2023
Describe metabolism of bilirubin???
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Dec 26, 2023
Bilirubin metabolism refers to the process by which bilirubin, a yellow pigment derived from the breakdown of heme, is produced, transported, and eliminated from the body. It is an essential process for the removal of waste products from the breakdown of red blood cells.
1. Production: Bilirubin is formed from the breakdown of heme, which is primarily derived from the degradation of hemoglobin in aged or damaged red blood cells. This process occurs mainly in the reticuloendothelial system, particularly in the spleen and liver. Heme is converted into biliverdin by the enzyme heme oxygenase, releasing carbon monoxide and iron in the process. Biliverdin is then rapidly converted into bilirubin by the enzyme biliverdin reductase.
2. Unconjugated Bilirubin: The bilirubin produced is initially in an unconjugated or indirect form, which is insoluble in water and cannot be excreted by the kidneys. It binds to albumin in the blood and is transported to the liver.
3. Uptake by the Liver: In the liver, unconjugated bilirubin is taken up by hepatocytes through a carrier-mediated process. Once inside the hepatocytes, it is bound to intracellular proteins.
4. Conjugation: Within the hepatocytes, unconjugated bilirubin undergoes conjugation with glucuronic acid, a process catalyzed by the enzyme UDP-glucuronosyltransferase (UGT). This conjugation converts bilirubin into a water-soluble form known as conjugated or direct bilirubin.
5. Secretion: Conjugated bilirubin is then transported into the bile canaliculi, small ducts within the liver, by an ATP-dependent transporter called multidrug resistance-associated protein 2 (MRP2). It is then released into the bile, which is stored in the gallbladder.
6. Elimination: When needed, bile is released from the gallbladder into the small intestine, where conjugated bilirubin is further metabolized by bacteria. In the intestine, bilirubin is converted into urobilinogen, a colorless compound. Some urobilinogen is reabsorbed into the bloodstream and excreted by the kidneys, giving urine its characteristic yellow color. The remaining urobilinogen is oxidized to form stercobilin, which gives feces its brown color.
In summary, bilirubin metabolism involves the production of bilirubin from heme breakdown, its uptake and conjugation in the liver, secretion into bile, and subsequent elimination through the intestines and kidneys. Any disruption in this process can lead to bilirubin-related disorders, such as jaundice or liver diseases.
1. Production: Bilirubin is formed from the breakdown of heme, which is primarily derived from the degradation of hemoglobin in aged or damaged red blood cells. This process occurs mainly in the reticuloendothelial system, particularly in the spleen and liver. Heme is converted into biliverdin by the enzyme heme oxygenase, releasing carbon monoxide and iron in the process. Biliverdin is then rapidly converted into bilirubin by the enzyme biliverdin reductase.
2. Unconjugated Bilirubin: The bilirubin produced is initially in an unconjugated or indirect form, which is insoluble in water and cannot be excreted by the kidneys. It binds to albumin in the blood and is transported to the liver.
3. Uptake by the Liver: In the liver, unconjugated bilirubin is taken up by hepatocytes through a carrier-mediated process. Once inside the hepatocytes, it is bound to intracellular proteins.
4. Conjugation: Within the hepatocytes, unconjugated bilirubin undergoes conjugation with glucuronic acid, a process catalyzed by the enzyme UDP-glucuronosyltransferase (UGT). This conjugation converts bilirubin into a water-soluble form known as conjugated or direct bilirubin.
5. Secretion: Conjugated bilirubin is then transported into the bile canaliculi, small ducts within the liver, by an ATP-dependent transporter called multidrug resistance-associated protein 2 (MRP2). It is then released into the bile, which is stored in the gallbladder.
6. Elimination: When needed, bile is released from the gallbladder into the small intestine, where conjugated bilirubin is further metabolized by bacteria. In the intestine, bilirubin is converted into urobilinogen, a colorless compound. Some urobilinogen is reabsorbed into the bloodstream and excreted by the kidneys, giving urine its characteristic yellow color. The remaining urobilinogen is oxidized to form stercobilin, which gives feces its brown color.
In summary, bilirubin metabolism involves the production of bilirubin from heme breakdown, its uptake and conjugation in the liver, secretion into bile, and subsequent elimination through the intestines and kidneys. Any disruption in this process can lead to bilirubin-related disorders, such as jaundice or liver diseases.
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