Enterohepatic Circulation and Health

by Kevin Ahern, PhD

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    So I've previously talked about how bilirubin is involved in that cycle of converting reactive oxygen species, and that's a recycling that's happening in the bilirubin and biliverdin in the process. With this slide, I want to talk about how it is that bilirubin is either eliminated through the feces and urine or how it's recycled using the portal system of the body. The process starts as before with heme being converted in the biliverdin and biliverdin being converted in the bilirubin as we can see here. Conjugation of the bilirubin creates bilirubin diglucuronide which is necessary for the bilirubin to be soluble in the bile system as we can see here. So the movement of bilirubin through the system involves the conjugation of bilirubin to diglucuronide to solubilize it so that it can appear in the bile. Moving from bile, the bilirubin diglucuronide enters the intestinal system where it's metabolized by bacteria. These bacteria convert bilirubin diglucuronide into urobilinogen. Now the urobilinogen has a couple of different fates that it can undergo. One fate is to go through the portal system and be recycled back into biliverdin. Recycling is important because it saves additional things that the cell might need. Remember that converting a biliverdin to bilirubin and then going back was saving -- giving protection against reactive oxygen species. So, making more of that cycle might help if reactive oxygen species are a consideration. On the other hand, the urobilinogen can pass through the intestinal system and be oxidized. Well it's, in this case, coverted into molecule known as stercobilin. And stercobilin is the molecule that gives feces the color that it has. Instead of being recycled, urobilinogen can also be oxidized. Now, oxidization produces compound called stercobilin. And stercobilin, whose structure as you can see on the...

    About the Lecture

    The lecture Enterohepatic Circulation and Health by Kevin Ahern, PhD is from the course Amino Acid Metabolism.

    Included Quiz Questions

    1. Intestinal bacteria convert it to stercobilin.
    2. Stercobilin gives urine its color.
    3. Biliary obstruction results in darker faeces and lighter urine.
    4. All of the answers are true.
    5. None of the answers are true.
    1. It is usually high in concentration in the liver or pancreatic diseases.
    2. It is consumed by intestinal flora.
    3. It causes jaundice only when its unconjugated form is increased.
    4. All of the answers are true.
    5. None of the answers are true.

    Author of lecture Enterohepatic Circulation and Health

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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    By Azwer A. on 06. April 2017 for Enterohepatic Circulation and Health

    I was impressed by the knowledge of the professor. However, the very short length of each lecture was disturbing and distracting.