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Questions and Answers
What is the primary function of liver function tests?
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?
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?
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?
What is the purpose of liver function tests in distinguishing liver disorders?
Which of the following is NOT a routine liver function test?
Which of the following is NOT a routine liver function test?
What is the advantage of liver function tests?
What is the advantage of liver function tests?
What is the normal range of total bilirubin in serum?
What is the normal range of total bilirubin in serum?
What is the product of haem catabolism?
What is the product of haem catabolism?
What is the function of biliverdin reductase in bilirubin production?
What is the function of biliverdin reductase in bilirubin production?
What is the difference between conjugated and unconjugated bilirubin?
What is the difference between conjugated and unconjugated bilirubin?
What is the amount of bilirubin formed per day?
What is the amount of bilirubin formed per day?
What is the role of albumin in bilirubin metabolism?
What is the role of albumin in bilirubin metabolism?
What is the primary way in which unconjugated bilirubin is transported to the liver?
What is the primary way in which unconjugated bilirubin is transported to the liver?
What is required for the facilitated diffusion of unconjugated bilirubin into the hepatocyte?
What is required for the facilitated diffusion of unconjugated bilirubin into the hepatocyte?
What is the enzyme that catalyzes the conjugation of bilirubin with glucoronic acid?
What is the enzyme that catalyzes the conjugation of bilirubin with glucoronic acid?
What is the form of bilirubin that is secreted into the bile canaliculi?
What is the form of bilirubin that is secreted into the bile canaliculi?
What is the direction of transport of conjugated bilirubin into the bile canaliculi?
What is the direction of transport of conjugated bilirubin into the bile canaliculi?
What is the rate-limiting step in bilirubin metabolism?
What is the rate-limiting step in bilirubin metabolism?
What is a possible indication of abnormally low albumin content?
What is a possible indication of abnormally low albumin content?
In which type of hepatitis is albumin level most likely to be decreased?
In which type of hepatitis is albumin level most likely to be decreased?
What is the role of the reticuloendothelial system in liver function testing?
What is the role of the reticuloendothelial system in liver function testing?
Which enzyme is a biomarker of hepatobiliary obstruction?
Which enzyme is a biomarker of hepatobiliary obstruction?
What is the relationship between albumin levels and liver function?
What is the relationship between albumin levels and liver function?
What type of disorders are characterized by chronic autoimmune disorders with predominant hepatic or biliary manifestations?
What type of disorders are characterized by chronic autoimmune disorders with predominant hepatic or biliary manifestations?
Which enzyme is found in cell membranes of many tissues, mainly in the liver, kidney, and pancreas?
Which enzyme is found in cell membranes of many tissues, mainly in the liver, kidney, and pancreas?
Which of the following pairs of plasma enzymes are most sensitive in diagnosing hepatobiliary diseases?
Which of the following pairs of plasma enzymes are most sensitive in diagnosing hepatobiliary diseases?
What is the primary function of albumin in the vascular system?
What is the primary function of albumin in the vascular system?
What is the approximate half-life of albumin?
What is the approximate half-life of albumin?
What is the significance of albumin in the early stages of acute hepatitis?
What is the significance of albumin in the early stages of acute hepatitis?
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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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