Conjugated Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Conjugated and links to relevant pages within the course.
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| Bilirubin Characterization Bilirubin, a product of hemoglobin breakdown, is characterized by its yellow pigment. The presence of bilirubin in urine is always abnormal. It is important to note that unconjugated bilirubin cannot be excreted by the kidneys because it is bound to albumin and is not soluble in water. In the liver, bilirubin combines with glucuronic acid through the action of a glucuronyl transferase to form water soluble bilirubin diglucuronide. Under normal circumstances, conjugated bilirubin passes from the bile duct and then to the intestinal tract. Intestinal bacteria reduce conjugated bilirubin to urobilinogen. Approximately half of the urobilinogen is excreted in the feces; most of the other half is recirculated through the liver. A small amount of urobilinogen bypasses the liver and is excreted in the urine. | View Page |
| Clinical Significance Liver damage or an obstructed bile duct allows conjugated bilirubin to enter the circulation and ultimately to appear in the urine. Patients with clinical jaundice due to hepatitis or cirrhosis will have bilirubinuria. If the jaundice is due to red cell destruction, there is an increase in unconjugated bilirubin which the kidneys cannot excrete. | View Page |
| When a patient has a bile duct obstruction, the bilirubin test portion of the reagent strip is: | View Page |
| Elevation in conjugated bilirubin is most likely to be found in which of the following conditions: | View Page |
| Which of the following conditions would be suggested by a marked rise in alkaline
phosphatase, jaundice, and a moderate rise in ALT: | View Page |
| Urine Bilirubin Bilirubin is formed as a result of the breakdown of hemoglobin from erythrocytes in the reticuloendothelial system. It becomes bound to albumin and transported through the blood to the liver. This free or unconjugated bilirubin is insoluble in water and cannot be filtered through the glomerulus of the kidney. In the liver, bilirubin becomes conjugated with glucuronic acid to form bilirubin diglucuronide. This conjugated bilirubin, which is also called direct bilirubin, is water soluble and is excreted by the liver through the bile duct and into the duodenum. | View Page |
| Urine Bilirubin Normally, small amounts of conjugated bilirubin, regurgitate back from the bile duct and enter the blood stream, so small amounts of conjugated bilirubin can be found in the plasma. Since conjugated bilirubin is not bound to protein, it is easily filtered through the glomerulus and excreted in the urine whenever the plasma level is increased. Normally, no detectable amount of bilirubin (sometimes referred to as “bile”) is found in the urine. | View Page |
| Chemiluminescence Chemiluminescent assays use antibodies that are conjugated to enzymes, such as peroxidase or alkaline phosphatase. These enzymes, mixed with chemiluminescent substrates, produce light in the visible spectrum. A direct relationship exists between the amount of drug that is present in the sample and the light units that are produced and measured by the luminometer in the instrument. Assays that use chemiluminescence are more sensitive than immunoassays that rely on the generation of a colored product. | View Page |