What happens to conjugated bilirubin in the small intestine?

What happens to conjugated bilirubin in the small intestine?

• A. It is absorbed into the bloodstream
• B. It is converted to urobilinogen
• C. It is retained in the liver
• D. It is expelled through urine

Answer: (B)

Conjugated bilirubin, which is water-soluble, is primarily secreted into the small intestine as part of bile. In the intestinal lumen, conjugated bilirubin undergoes microbial reduction and is converted into urobilinogen. This process occurs largely because bacteria in the gut can break down conjugated bilirubin into urobilinogen through enzymatic reactions. Urobilinogen can then take several pathways. Some of it is reabsorbed into the bloodstream and transported back to the liver, where it can be reused or excreted via bile. A portion of urobilinogen is also oxidized to form urobilin, which gives feces its characteristic brown color. This transformation is essential because it indicates that bilirubin is being metabolized effectively by intestinal flora, and it's a crucial part of the bilirubin metabolism process. While other options might suggest alternative fates for conjugated bilirubin, they do not align with the typical physiological processes occurring in the small intestine. Understanding this metabolic pathway is vital for those studying biochemistry and pathology related to the liver and bile, ensuring a comprehensive grasp of bilirubin's role in digestion and excretion.

Conjugated bilirubin, which is water-soluble, is primarily secreted into the small intestine as part of bile. In the intestinal lumen, conjugated bilirubin undergoes microbial reduction and is converted into urobilinogen. This process occurs largely because bacteria in the gut can break down conjugated bilirubin into urobilinogen through enzymatic reactions.

Urobilinogen can then take several pathways. Some of it is reabsorbed into the bloodstream and transported back to the liver, where it can be reused or excreted via bile. A portion of urobilinogen is also oxidized to form urobilin, which gives feces its characteristic brown color. This transformation is essential because it indicates that bilirubin is being metabolized effectively by intestinal flora, and it's a crucial part of the bilirubin metabolism process.

While other options might suggest alternative fates for conjugated bilirubin, they do not align with the typical physiological processes occurring in the small intestine. Understanding this metabolic pathway is vital for those studying biochemistry and pathology related to the liver and bile, ensuring a comprehensive grasp of bilirubin's role in digestion and excretion.