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Essential Biochemistry - Hemoglobin Metabolism (Section 3)

1
What is the precursor for heme synthesis?
Answer
(C)
Glycine
2
Which of the following is a characteristic of obstructive jaundice?
Answer
A
B
D
3
The characteristic brown color of stool is due to:
Answer
(D)
Stercobilin
4
The oxidation of protoporphyrin-IX to protoporphyrin-IX di-oxide is catalyzed by:
Answer
(A)
Heme oxygenase
5
The measurement of serum bilirubin levels is essential for the diagnosis of:
Answer
(C)
Jaundice
6
Which of the following is a key characteristic of Crigler-Najjar syndrome?
Answer
(B)
Deficiency in UDP-glucuronosyltransferase
7
Which enzyme is deficient in congenital erythropoietic porphyria?
Answer
(B)
Uroporphyrinogen III synthase
8
The first committed step in heme synthesis is catalyzed by which enzyme?
Answer
(A)
ALA synthase
9
The enzyme responsible for conjugating bilirubin in the liver is:
Answer
(A)
UDP-glucuronosyltransferase
10
The formation of porphobilinogen (PBG) occurs by the action of:
Answer
(B)
Porphobilinogen deaminase
11
Which enzyme is deficient in the type 1 Crigler-Najjar syndrome?
Answer
(A)
UDP-glucuronosyltransferase
12
In the context of jaundice, what does 'conjugated' mean?
Answer
(B)
Bound to glucuronic acid
13
What is the primary function of bilirubin?
Answer
(B)
Excreting waste products of heme metabolism
14
In which condition is the production of heme synthesis inhibited?
Answer
(D)
Lead poisoning
15
Which of the following would you expect to find increased in the urine of a patient with obstructive jaundice?
Answer
(B)
Conjugated bilirubin
16
The formation of bilirubin from heme involves what enzyme?
Answer
(B)
Heme oxygenase
17
Which of the following is a component of heme?
Answer
(C)
Iron
18
What causes jaundice?
Answer
(A)
An increase in serum bilirubin levels
19
In the liver, the bilirubin is derived from breakdown of ______.
Answer
(B)
Hemoglobin
20
Which of the following is not a cause of jaundice?
Answer
(D)
Increased hemoglobin
21
What is the major cause of jaundice?
Answer
(B)
Increased levels of bilirubin
22
Which step of heme synthesis is inhibited by lead?
Answer
(B)
ALA dehydratase
23
Which of the following are not used to diagnose jaundice?
Answer
(D)
Serum hemoglobin levels
24
Which type of jaundice is characterized by an absence of urobilinogen in the urine?
Answer
(C)
Obstructive jaundice
25
What is the main site of bilirubin conjugation?
Answer
(A)
Liver
26
What is the normal range of conjugated bilirubin in serum (approximately)?
Answer
(A)
0.1 to 0.4 mg/dL
27
Which of the following is NOT a characteristic of hemolytic jaundice?
Answer
(D)
Increased conjugated bilirubin
28
What causes the dark color of urine in patients with porphyria?
Answer
(C)
Excess porphyrins
29
Which condition is associated with black urine?
Answer
(C)
Acute intermittent porphyria
30
Heme is the prosthetic group of several proteins and enzymes, including:
Answer
A
B
C
D
31
What is the end product of heme catabolism?
Answer
(B)
Bile pigment
32
In Gilbert's syndrome, which of the following is TRUE?
Answer
(C)
There is a mild defect in bilirubin conjugation.
33
Which enzyme is deficient in acute intermittent porphyria?
Answer
(A)
Uroporphyrinogen I synthase
34
What is the name of the enzyme that converts biliverdin to bilirubin?
Answer
(B)
Biliverdin reductase
35
The initial reaction in heme synthesis that occurs in mitochondria is catalyzed by:
Answer
(A)
ALA synthase
36
What is the role of heme oxygenase?
Answer
(B)
Converts heme to biliverdin
37
Which type of jaundice is associated with an increase in unconjugated bilirubin due to excessive hemolysis?
Answer
(A)
Hemolytic jaundice