Biochemistry week 16 Flashcards
what is the structure of heme
- Composed of protoporphyrin IX and ferrous iron
- 4 pyrrole rings
What is heme required for
Hemoglobin synthesis
Where does heme synthesis occur
Liver
Where is heme produce
In the long bones
When heme is produced for cytochrome synthesis what is it called
- Hepatic system
Why is cytochrome synthesis important
- For cytochrome P450 in the liver
Name the first 4 end produts in the heme synthesis reactions
- Aminolevlinic Acid
- porphobilinogen
-uroporphyrinogen 1
-uroporphyrinogen 111
Where is bile produced
Liver
Where is bile stored
Gallbladder
When and where is bile excreted
- Duodenum after a meal
What is the function of bile salts
They are needed for lipid absorption
What is the function of bilirubin
- It is the mode of excretion for heme breakdwon products
Where does bilirubin metabolism/breakdown occur
Liver and spleen
Explain the process of Bilirubin formation
(Starting from heme)
-Heme oxygenase in macrophages of the mononuclear phagocyte system (MPS) converts heme to biliverdin (green pigment).
-Produces carbon monoxide (CO) and releases Fe²⁺.
-Biliverdin is reduced to bilirubin
Bilirubin and its derivatives are called bile pigments.
Explain the process of bilirubin uptake by the live , starting with albumin
Bilirubin binds noncovalently to albumin in the blood.
Explain how bilirubin enters the hepatocytes
Bilirubin dissociates from albumin, enters liver cells by facilitated diffusion, and binds to ligandin
How is billirubin Diglucuroninde formed
- 2 glucuronic acid molecules are added to bilirubin
Is conjugated bilirubin transported into bile
Yes
Is Unconjugated bilirubin transported into bile
- No
Explain how urobilinogen is formed in the intestines,starting with conjugated bilirubin(CB)
-CB is hydrolyzedand reduced by gut bacteria forming urobilinogen
What is Jaundice caused by
- Hyperbilirubinemia
What are symptoms of Jaundice
- Yellow discoloration of the skin, nails and sclerae due to bilirubin deposition
Name the types of Jaundice
-Prephatic
-Intrahepatic
-Posthepatic
What is prehaptic jaundice caused by
-Excess bilirubin production due to excessive hemolysis producing bilirubin faster than it can be conjugated
What is intrahepatic jaundice caused by
- Liver damage
What can intrahepatic jaundice cause
Unconjugated hyperbilirubinemia due to decreased conjugation
What are the symtoms of intrahepatic jaundice
- Dark urine
-Pale, clay-coloured stools
-Elevated alanine
What is posthepatic jaundice caused by
- Bile duct obstruction
What does posthepatic jaundice lead to
- Conjugated hyperbilirubinemia as conjugated bilirubin cannot enter the intestines
What are symptoms of Posthepatic jaundice
- Nausea
-Dark urine
-Pale, clay coloured stools
Name the 4 genetic disorders that impaire bilirubin conjugation and secretion
- Gilbert syndrome
-Cirger -Najjar syndrome
-Dubin-Johnson and Rotors syndrome
