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WorksheetsQuiz on Heme Metabolism
Total questions: 10
Worksheet time: 5mins
Which of the following statements about hemoglobin is correct?
A. Hemoglobin consists of four heme groups and four identical beta chains.
B. Iron in heme binds irreversibly to oxygen.
C. Hemoglobin has four polypeptide chains: two alpha and two beta.
D. Hemoglobin is found only in the liver.
Which of the following is not a hemeprotein?
A. Myoglobin
B. Cytochrome P450
C. Insulin
D. Catalase
Which of the following statements about porphyrias is incorrect?
A. Porphyrias are caused by enzyme defects in the heme biosynthetic pathway.
B. ALA and PBG accumulation can lead to neurovisceral symptoms.
C. All porphyrias are caused by loss-of-function mutations.
D. Porphyrins accumulating in skin can cause photosensitivity.
Which of the following is true about indirect (unconjugated) bilirubin?
A. It is water-soluble and excreted in urine.
B. It is conjugated with glucuronic acid in the spleen.
C. It binds to albumin in the bloodstream.
D. It is yellow due to stercobilin.
Which of the following about heme degradation is false?
A. Heme is broken down to biliverdin, then to bilirubin.
B. Conjugated bilirubin is formed in the spleen.
C. Stercobilin gives feces its brown color.
D. Heme oxygenase is responsible for the oxidative cleavage of the heme ring.
A patient presents with abdominal pain, reddish-colored urine, and no signs of liver dysfunction. Urine tests show elevated PBG and ALA levels. What is the most likely diagnosis?
A. Obstructive jaundice
B. Acute intermittent porphyria
C. Hemolytic anemia
D. Gilbert syndrome
A 3-day-old infant develops jaundice. Lab results show elevated unconjugated bilirubin. Which of the following is the most likely cause?
A. Liver cirrhosis
B. Biliary obstruction
C. Physiological immaturity of UDP-glucuronosyltransferase
D. Increased stercobilin in urine
A man with a history of lead exposure has high levels of ALA in urine and free erythrocyte protoporphyrin. Which enzyme is most likely inhibited?
A. Heme oxygenase
B. UDP-glucuronosyltransferase
C. ALA synthase
D. Ferrochelatase
A patient's stool is pale, and urine is dark-colored. Which of the following is the most likely underlying issue?
A. Hemolysis
B. Liver failure
C. Obstruction of bile duct
D. Decreased ALA synthase activity
A patient with a liver tumor has conjugated hyperbilirubinemia. What is the most likely explanation for the presence of bilirubin in urine?
A. Direct bilirubin is water-insoluble
B. Indirect bilirubin leaks into urine when hepatocytes die
C. Conjugated bilirubin is water-soluble and appears in urine when bile excretion is blocked
D. Only stercobilin is responsible for urine color
