heme is the portion of hemoglobin associated with the production of bilirubin.
heme is the portion of hemoglobin associated with the production of bilirubin.
portion of hemoglobin associated with the production of bilirubin?
heme
when red blood cells have completed their life span of approximately 120 days, or when they are damaged, their membranes become fragile and prone to rupture. as each red blood cell traverses through the reticuloendothelial system, its cell membrane ruptures when its membrane is fragile enough to allow this. cellular contents, including hemoglobin, are subsequently released into the blood. the hemoglobin is phagocytosed by macrophages, and split into its heme and globin portions. the globin portion, a protein, is degraded into amino acids and plays no role in jaundice. two reactions then take place with the heme molecule. the first oxidation reaction is catalyzed by the microsomal enzyme heme oxygenase and results in biliverdin (green color pigment), iron and carbon monoxide. the next step is the reduction of biliverdin to a yellow color tetrapyrol pigment called bilirubin by cytosolic enzyme biliverdin reductase. this bilirubin is "unconjugated," "free" or "indirect" bilirubin. approximately 4 mg of bilirubin per kg of blood is produced each day. the majority of this bilirubin comes from the breakdown of heme from expired red blood cells in the process just described. approximately twenty percent comes from other heme sources, however, including ineffective erythropoiesis, and the breakdown of other heme-containing proteins, such as muscle myoglobin and cytochromes.
jaundice
note: conjugated bilirubin is often incorrectly called "direct bilirubin" and unconjugated bilirubin is incorrectly called "indirect bilirubin". direct and indirect refer solely to how compounds are measured or detected in solution. direct bilirubin is any form of bilirubin which is water-soluble and is available in solution to react with assay reagents; direct bilirubin is often made up largely of conjugated bilirubin, but some unconjugated bilirubin (up to 25%) can still be part of the "direct" bilirubin fraction. likewise, not all conjugated bilirubin is readily available in solution for reaction or detection (for example, if it is hydrogen bonding with itself) and therefore would not be included in the direct bilirubin fraction.
bilirubin