Breakdown and Recycling Processes
Posted: Wednesday, March 9th, 2022 | Updated: August 31st, 2022
Posted: Wednesday, March 9th, 2022 | Updated: August 31st, 2022
Hemoglobin Catabolism and Bilirubin Metabolism
Red blood cells are broken down by the spleen, bone marrow, and the liver by macrophages. Hemoglobin separates into heme and globin. Globin is essentially protein and is broken down into amino acids and used within the body and for erythropoiesis once again. Heme is further broken down into iron and biliverdin. Like globin, iron is reused within the body for erythropoiesis. Biliverdin becomes unconjugated bilirubin which needs to be transported by albumin to the liver because it is lipid soluble. It is toxic if it builds up. Hence, it needs to be removed. In the liver, the bilirubin becomes conjugated and becomes water soluble. It is excreted by the liver in bile which is released into the duodenum through the common bile duct. Bile contains conjugated bilirubin, bile salts, and other digestive enzymes. Bile is stored in the gallbladder and excreted into the small intestine for the digestion of lipids. The conjugated bilirubin travels to the colon where it becomes urobilinogen or stercobilinogen. Bacteria within the ileum will convert the conjugated bilirubin to urobilinogen. This is lipid soluble and some will be reabsorbed into the bloodstream. It once again gets bound to albumin for transportation to the liver to be either excreted by the kidneys in the urine as urobilin or in the bile once again. The majority of urobilinogen is oxidized by bacteria and turned into stercobilins which are excreted in the feces and provides the brown pigment typically seen
Ammonia Breakdown
When protein is broken down, ammonia is produced. Proteins are made up of amino acid chains. The liver converts ammonia to urea. Urea is excreted by the kidneys and into the urine. When the liver is unable to convert ammonia into urea, ammonia levels within the blood increase. Therefore, patients may show signs of hepatic encephalopathy. Low protein diets are recommended in these situations. When the kidneys are unable to excrete the urea, patients may will likely have elevated levels of blood urea nitrogen
Red blood cells are broken down by the spleen, bone marrow, and the liver by macrophages. Hemoglobin separates into heme and globin. Globin is essentially protein and is broken down into amino acids and used within the body and for erythropoiesis once again. Heme is further broken down into iron and biliverdin. Like globin, iron is reused within the body for erythropoiesis. Biliverdin becomes unconjugated bilirubin which needs to be transported by albumin to the liver because it is lipid soluble. It is toxic if it builds up. Hence, it needs to be removed. In the liver, the bilirubin becomes conjugated and becomes water soluble. It is excreted by the liver in bile which is released into the duodenum through the common bile duct. Bile contains conjugated bilirubin, bile salts, and other digestive enzymes. Bile is stored in the gallbladder and excreted into the small intestine for the digestion of lipids. The conjugated bilirubin travels to the colon where it becomes urobilinogen or stercobilinogen. Bacteria within the ileum will convert the conjugated bilirubin to urobilinogen. This is lipid soluble and some will be reabsorbed into the bloodstream. It once again gets bound to albumin for transportation to the liver to be either excreted by the kidneys in the urine as urobilin or in the bile once again. The majority of urobilinogen is oxidized by bacteria and turned into stercobilins which are excreted in the feces and provides the brown pigment typically seen
Ammonia Breakdown
When protein is broken down, ammonia is produced. Proteins are made up of amino acid chains. The liver converts ammonia to urea. Urea is excreted by the kidneys and into the urine. When the liver is unable to convert ammonia into urea, ammonia levels within the blood increase. Therefore, patients may show signs of hepatic encephalopathy. Low protein diets are recommended in these situations. When the kidneys are unable to excrete the urea, patients may will likely have elevated levels of blood urea nitrogen
Sources:
"Bilirubin Metabolism." Armando Hasudungan, 24 Apr. 2022, Youtube, www.youtube.com/watch?v=_-JFqnBYmzc.
"Bilirubin Metabolism." Armando Hasudungan, 24 Apr. 2022, Youtube, www.youtube.com/watch?v=_-JFqnBYmzc.