Y1S2 011 I Biochem Bilirubin and Liver Function

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Questions and Answers

What is the primary function of liver function tests?

To diagnose a specific liver disease

To assess the functional hepatic cell activity

To detect the presence of liver disease and monitor its progression (correct)

To provide a cheap and non-invasive method of therapy

Which of the following enzymes is a biomarker of liver injury?

GGT

ALT (correct)

ALP

5'nucleotidase

What is the characteristic of the liver that allows it to tolerate a significant amount of damage before symptoms appear?

Liver regeneration

Liver cirrhosis

Liver inflammation

Functional reserve (correct)

What is the purpose of liver function tests in distinguishing liver disorders?

To differentiate between acute viral hepatitis and chronic liver disease Signup and view all the answers

Which of the following is NOT a routine liver function test?

5'nucleotidase Signup and view all the answers

What is the advantage of liver function tests?

They are cheap and non-invasive Signup and view all the answers

What is the normal range of total bilirubin in serum?

4 - 18 µmol/L Signup and view all the answers

What is the product of haem catabolism?

Bilirubin Signup and view all the answers

What is the function of biliverdin reductase in bilirubin production?

Reduces biliverdin to unconjugated bilirubin Signup and view all the answers

What is the difference between conjugated and unconjugated bilirubin?

Conjugated bilirubin is water-soluble, while unconjugated bilirubin is insoluble in water Signup and view all the answers

What is the amount of bilirubin formed per day?

300 mg Signup and view all the answers

What is the role of albumin in bilirubin metabolism?

Albumin binds to unconjugated bilirubin in the blood Signup and view all the answers

What is the primary way in which unconjugated bilirubin is transported to the liver?

Bound to albumin in plasma Signup and view all the answers

What is required for the facilitated diffusion of unconjugated bilirubin into the hepatocyte?

Inorganic anions, such as Cl- Signup and view all the answers

What is the enzyme that catalyzes the conjugation of bilirubin with glucoronic acid?

Uridine diphosphate (UDP) glucuronosyltransferase Signup and view all the answers

What is the form of bilirubin that is secreted into the bile canaliculi?

Conjugated bilirubin Signup and view all the answers

What is the direction of transport of conjugated bilirubin into the bile canaliculi?

Uni-directional Signup and view all the answers

What is the rate-limiting step in bilirubin metabolism?

Secretion of conjugated bilirubin into the bile canaliculi Signup and view all the answers

What is a possible indication of abnormally low albumin content?

Kidney disease Signup and view all the answers

In which type of hepatitis is albumin level most likely to be decreased?

Chronic active hepatitis Signup and view all the answers

What is the role of the reticuloendothelial system in liver function testing?

Bilirubin metabolism Signup and view all the answers

Which enzyme is a biomarker of hepatobiliary obstruction?

GGT Signup and view all the answers

What is the relationship between albumin levels and liver function?

Albumin levels are inversely proportional to liver function Signup and view all the answers

What type of disorders are characterized by chronic autoimmune disorders with predominant hepatic or biliary manifestations?

Inflammatory hepatobiliary diseases Signup and view all the answers

Which enzyme is found in cell membranes of many tissues, mainly in the liver, kidney, and pancreas?

Gamma-glutamyltransferase Signup and view all the answers

Which of the following pairs of plasma enzymes are most sensitive in diagnosing hepatobiliary diseases?

Alkaline phosphatase and Gamma-glutamyltransferase Signup and view all the answers

What is the primary function of albumin in the vascular system?

Maintaining osmotic pressure Signup and view all the answers

What is the approximate half-life of albumin?

20 days Signup and view all the answers

What is the significance of albumin in the early stages of acute hepatitis?

It is a poor indicator of disease progression Signup and view all the answers

Study Notes

Bilirubin Production and Metabolism

Bilirubin is the yellow breakdown product of normal haem catabolism
About 300 mg of bilirubin is formed per day
Bilirubin is the breakdown product of the haem moiety of haemoglobin, other haemoproteins, and a small pool of free haem

Formation of Unconjugated Bilirubin

Haem oxygenase converts haem to biliverdin, which is reduced to unconjugated bilirubin by biliverdin reductase
The α-methene bridge carbon is eliminated as CO and the iron molecule is released
Three molecules of oxygen are consumed in this reaction and NADPH is required

Transport of Bilirubin to the Liver

Unconjugated bilirubin circulates in the plasma bound to albumin (unconjugated-albumin complex)
At the sinusoidal surface of the hepatocyte, unconjugated bilirubin dissociates from albumin and is taken up by the hepatocyte by facilitated diffusion that requires inorganic anions, such as Cl-
Ligandin carries bilirubin from the cytosol into the smooth endoplasmic reticulum of the hepatocytes

Conjugation of Bilirubin

In the smooth endoplasmic reticulum, bilirubin is conjugated with glucoronic acid, a reaction catalyzed by uridine diphosphate (UDP) glucuronosyltransferase to form mono- and di-glucuronides of bilirubin (conjugated bilirubin)

Secretion of Conjugated Bilirubin

Mono- and di-glucuronides of bilirubin (conjugated bilirubin) are water-soluble and secreted (along with bile salts) into the bile canaliculi, eventually reaching the small intestine via the ducts of the biliary system
Conjugated bilirubin undergoes unidirectional transport into the bile against a concentration gradient

Liver Function Tests

Functions of the liver include bilirubin production and metabolism
Routine liver function tests include enzymes (ALT, AST, ALP, GGT) and albumin along with direct and total bilirubin
Liver function tests provide information about the state of a patient's liver

Albumin

Albumin is a protein made only by the liver and excreted by the kidneys
Albumin is essential for maintaining the osmotic pressure in the vascular system
Albumin is also important in the transportation of many substances such as drugs, lipids, and hormones
Albumin has a half-life of approximately 20 days

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Description

Test your knowledge of bilirubin levels, including direct and total bilirubin, and how they relate to liver function. Learn about the normal serum bilirubin levels and how to calculate indirect bilirubin. This quiz is perfect for students of medicine, biology, and biochemistry.