Heme Metab MCQ

Question 1

During hemoglobin recycling in the spleen, heme is initially converted into:

a. Bilirubin
b. Biliverdin
c. Urobilin
d. Urobilinogen

Answer 1

b. Biliverdin
The pathway for the breakdown for heme is as follows: Heme → Biliverdin → Bilirubin (reticuloendothelial system) → Further processing

Question 2

Microsomal heme oxygenase system catalyses the first step in the degradation of heme, converting it to

a. Protoporphyrin III
b. Porphin
c. Bilirubin
d. Biliverdin
e. Bilirubin diglucuronide

Answer 2

d. Biliverdin

Heme → Biliverdin → Bilirubin (reticuloendothelial system) → Further processing

Question 3

3. The heme portion of hemoglobin is eventually:
   a. Converted into stercobilin in the large intestine
   b. Converted into urobilin in the kidney
   c. Excreted from the body
   d. None of the above
   e. All of the above

Answer 3

e. All of the above

Heme → Biliverdin → Bilirubin (reticuloendothelial system)→ Bilirubin diglucuronide (conjugation occurs in the liver)→ Urobilinogen (conversion by bacteria in the gut)→ Urobilin/Stercobilin (urobilin for urinary system – kidneys, stercobilin in feces)
Stercobilin and urobilin are eventually excreted from the body in feces and urine respectively.

Question 4

4. The Fe3+ portion of hemoglobin is eventually:
   a. Converted into transferrin in the large intestine
   b. Converted into ferritin in the kidney
   c. Excreted from the body
   d. None of the above
   e. All of the above

Answer 4

d. None of the above
Fe3+ in hemoglobin is termed methemoglobin, which is unable to bind oxygen. It normally exists in the body as 1-2% of total hemoglobin. It is reconverted to normal hemoglobin, with iron in the ferrous, Fe2+ state by methemoglobin reductase. The iron portion of hemoglobin is then eventually recycled. Hence, none of the above options are correct.

Question 5

5. (Diagram of a liver and bile duct) There is an obstruction in the bile duct. Which of the following does not represent the bilirubin metabolism?
   a. This disease is called cholestasis.
   b. There is an increase in unconjugated bilirubin in the plasma
   c. There is a decrease in stercobilin
   d. There is an absence of urobilin and presence of bilirubin glucuronide in the urine

Answer 5

b. There is an increase in unconjugated bilirubin in the plasma
A: Obstruction in bile duct preventing flow of bile from liver to duodenum is cholestasis and can lead to obstructive jaundice.
B: There should be normal levels of unconjugated bilirubin in the plasma though levels of conjugated bilirubin would be expected to increase.
C & D: In obstructive jaundice, conjugated bilirubin in bile cannot enter the gut to be converted into urobilinogen. Lack of urobilinogen results in lack of sternobilin and urobilin. Conjugated bilirubin is also called bilirubin glucuronide and high levels in plasma can spill over into urine.
(*Note: Some sources might say that unconjugated bilirubin levels might rise slightly in the plasma in severe cases. Assuming this qn is not flawed, B remains best option.)

Question 6

6. The characteristic yellow colour of urine is due to
   a. Bilirubin
   b. Uroporphyrin I
   c. Uroporphyrin III
   d. Urobilinogen
   e. Urobilin

Answer 6

e. Urobilin

Question 7

Patient presents with intermittent abdominal pain and urine that darkens on exposure to light. investigations would MOST LIKELY show an accumulation of 
A. porphobilinogen
B. uroporphyrinogen III
C. protoporphyrin IX 
D. heme

Answer 7

A. porphobilinogen

Question 8

Patient presents with skin blistering of sun-exposed areas and reddish urine. Investigations would MOST LIKELY show an accumulation of 
A. uroporphyrinogen III 
B. coproporphyrinogen III
C. protoporphyrin IX 
D. heme

Answer 8

A. uroporphyrinogen III

qn is testing which porphyria is most common (all options can cause the symptoms)

Question 9

The brownish colouration of stools is due to the oxidation of: 
A. unconjugated bilirubin 
B. conjugated bilirubin 
C. urobilinogen 
D. urobilin
E. stercobilin

Answer 9

C. urobilinogen

qn says “oxidation of”

Question 10

Patient with hemolysis
A. increased conjugated bilirubin
B. increased AST/ALT 
C. decreased urobilinogen 
D. decreased haptoglobin

Answer 10

D. decreased haptoglobin

Question 11

Patient with a stone obstructing bile duct
A. decreased conjugated bilirubin 
B. decreased stercobilin
C. increased urobilinogen 
D. increased hemoglobinuria

Answer 11

B. decreased stercobilin

Question 12

Patient diagnosed with acute viral hepatitis
A. decreased conjugated bilirubin
B. decreased haptoglobin
C. increased AST/ALT 
D. increased ALP/GGT

Answer 12

C. increased AST/ALT

not A bc it’s “acute” - hasnt had time to release so much stuff yet

Question 13

Patient with high levels of HbF and HbA has:
A. alpha thalassemia
B. beta thalassemia

Answer 13

B. beta thalassemia

Question 14

Blood and urine investigations in a patient with thalassemia major
A. high conjugated bilirubin, high urobilinogen
B. high conjugated bilirubin, low urobilinogen
C. high unconjugated bilirubin, high urobilinogen
D. high unconjugated bilirubin, low urobilinogen

Answer 14

C. high unconjugated bilirubin, high urobilinogen

Tha maj leads to hemolysis which is associated w pre-hepatic jaundice

Question 15

Patient on a strict vegan diet with low iron content
A. low DMT-1
B. low ferroportin
C. high ferritin
D. high transferrin binding capacity 
E. high hepcidin

Answer 15

D. high transferrin binding capacity

Question 16

Patient with thalassemia major on regular blood transfusion. Physical examination shows bronzing of skin. 
A. low plasma iron 
B. high transferrin binding capacity 
C. high ferritin levels 
D. low hepcidin levels 
E. high DMT-1

Answer 16

C. high ferritin levels