[MCQ] Porphyrias-Part 1

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Porphyrias-Part 1

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Question 1

Which of the following is a sporadic metabolic disorder ?

A	Porphyria cutanea tarda (PCT)
B	Acute intermittent porphyria (AIP)
C	Hereditary coproporphyria (HCP)
D	Variegate porphyria (VP)

Question 1 Explanation:

Porphyrias are metabolic disorders due to deficiency of a specific enzyme in heme biosynthetic pathway. Porphyria cutanea tarda (PCT) is a sporadic disorder. Rrest of the porphyrias are inherited either as autosomal dominant, autosomal recessive, or X-linked traits.

Question 2

The most common porphyria is ?

A	Porphyria cutanea tarda (PCT)
B	Acute intermittent porphyria (AIP)
C	Hereditary coproporphyria (HCP)
D	Variegate porphyria (VP)

Question 2 Explanation:

Porphyrias are either hepatic or erythropoietic, depending on the primary site of overproduction and accumulation of their respective porphyrin precursors. PCT is the most common porphyria. It is hepatic and presents with blistering cutaneous photosensitivity, which is usually a manifestation of the erythropoietic porphyrias.

Question 3

Major manifestation of the acute hepatic porphyrias is ?

A	Gastrointestinal
B	Skin
C	Neurologic
D	Endocrinal

Question 3 Explanation:

Major manifestations of acute hepatic porphyrias are neurologic (neuropathic abdominal pain, peripheral motor neuropathy, and mental disturbances

Question 4

Erythropoietic porphyrias usually present with ?

A	Gastrointestinal manifestations
B	Skin manifestations
C	Neurologic manifestations
D	Endocrinal manifestations

Question 4 Explanation:

Erythropoietic porphyrias usually present with cutaneous photosensitivity at birth or in early childhood, or in the case of congenital erythropoietic porphyria (CEP), even in utero as nonimmune hydrops fetalis. Cutaneous sensitivity to sunlight results from excitation of excess porphyrins in the skin by long-wave ultraviolet light, leading to cell damage, scarring, and disfigurement

Question 5

Heme biosynthesis involves how many enzymatic steps in the conversion of glycine & succinyl-CoA to heme ?

A	2
B	4
C	6
D	8

Question 5 Explanation:

Heme biosynthesis involves eight enzymatic steps in the conversion of glycine & succinyl-CoA to heme.

Question 6

Enzymes involved in heme biosynthesis are encoded by how many genes ?

A	4
B	7
C	9
D	12

Question 6 Explanation:

Enzymes involved in heme biosynthesis are encoded by nine genes. The first enzyme 5?- aminolevulinate synthase (ALA-synthase) has two genes.

Question 7

The first enzyme in the heme biosynthesis pathway is ?

A	5’-aminolevulinate synthase (ALA-synthase)
B	5’-aminolevulinate dehydratase (ALA-dehydratase)
C	Hydroxymethylbilane synthase (HMB-synthase or PBGdeaminase)
D	Uroporphyrinogen III synthase (URO-synthase)

Question 7 Explanation:

The first enzyme in the heme biosynthesis pathway is 5?-aminolevulinate synthase (ALA-synthase). It has two genes that encode unique housekeeping (ALAS1) and erythroid- specific (ALAS2) isozymes. The second enzyme, 5?-aminolevulinate dehydratase (ALA-dehydratase), third is

Question 8

Which of the following enzymes in the heme biosynthesis pathway is located in mitochondrion ?

A	5’-aminolevulinate synthase (ALA-synthase)
B	5’-aminolevulinate dehydratase (ALA-dehydratase)
C	Hydroxymethylbilane synthase (HMB-synthase or PBGdeaminase)
D	Uroporphyrinogen III synthase (URO-synthase)

Question 8 Explanation:

The first and last three enzymes in the pathway are located in the mitochondrion, whereas the other four are in the cytosol.

Question 9

Heme is required for synthesis of which of the following ?

A	Hemoglobin
B	Myoglobin
C	Cytochrome P450 enzymes (CYPs)
D	All of the above

Question 9 Explanation:

Heme is required for a variety of hemoproteins such as hemoglobin, myoglobin, respiratory cytochromes, and the cytochrome P450 enzymes (CYPs). Hemoglobin synthesis in erythroid precursor cells accounts for approximately 85% of daily heme synthesis in humans. Hepatocytes account for most of the rest, primarily for the synthesis of CYPs, which are especially abundant in the liver endoplasmic reticulum, and turn over more rapidly than many other hemoproteins, such as the mitochondrial respiratory cytochromes

Question 10

To confirm the diagnosis of porphyria, laboratory measurement of porphyrin precursors is done in which of the following ?

A	Urine
B	Plasma
C	Feces
D	All of the above

Question 10 Explanation:

Laboratory measurement of porphyrin precursors like 5?-aminolevulinic acid (ALA) and porphobilinogen (PBG) in urine, plasma, erythrocytes, or feces is required to confirm or exclude the diagnosis of porphyria.

Question 11

Which of the following is involved in the formation of ALA ?

A	Glycine
B	Pyridoxal phosphate
C	Succinyl coenzyme A
D	All of the above

Question 11 Explanation:

The first enzyme, ALA-synthase, catalyzes the condensation of glycine, activated by pyridoxal phosphate and succinyl coenzyme A, to form ALA.

Question 12

Which of the following enzymes catalyzes the condensation of two molecules of ALA to form PBG ?

A	5’-aminolevulinate synthase (ALA-synthase)
B	5’-aminolevulinate dehydratase (ALA-dehydratase)
C	Hydroxymethylbilane synthase (HMB-synthase or PBGdeaminase)
D	Uroporphyrinogen III synthase (URO-synthase)

Question 12 Explanation:

The second enzyme, 5?-aminolevulinate dehydratase (ALA-dehydratase), catalyzes the condensation of two molecules of ALA to form PBG.

Question 13

Head-to-tail condensation of how many PBG molecules forms HMB ?

A	1
B	2
C	3
D	4

Question 13 Explanation:

Hydroxymethylbilane synthase (HMB-synthase or PBG-deaminase) catalyzes head-to-tail condensation of four PBG molecules to form the linear tetrapyrrole, HMB.

Question 14

Which of the following enters mitochondrion via transporter ABCB6 ?

A	Porphobilinogen (PBG)
B	Uroporphyrinogen (URO’gen) III
C	Coproporphyrinogen (COPRO’gen) III
D	Protoporphyrinogen (PROTO’gen) IX

Question 14 Explanation:

The fifth enzyme, uroporphyrinogen decarboxylase (URO-decarboxylase), catalyzes the sequential removal of four carboxyl groups from acetic acid side chains of URO’gen III to form coproporphyrinogen (COPRO’gen) III, a tetracarboxylate porphyrinogen. Coproporphyrinogen (COPRO’gen) III enters mitochondrion via a specific transporter, ABCB6, where COPRO-oxidase, the sixth enzyme, catalyzes decarboxylation of two of the four propionic acid groups to form the two vinyl groups of protoporphyrinogen (PROTO’gen) IX, a decarboxylate porphyrinogen.

Question 15

PROTO-oxidase oxidizes PROTO IX’gen to protoporphyrin IX by the removal of ?

A	Acetic acid side chains
B	Propionic acid groups
C	Hydrogen atoms
D	Ferrous iron atoms

Question 15 Explanation:

PROTO-oxidase oxidizes PROTO IX’gen to protoporphyrin IX by the removal of six hydrogen atoms to form porphyrin (oxidized form).

Question 16

Ferrochelatase is also called ?

A	Heme decarboxylase
B	Heme synthase
C	Protoheme synthase
D	Protoheme ferrolyase

Question 16 Explanation:

Ferrous iron is inserted into protoporphyrin IX to form heme. This reaction is catalyzed by eighth enzyme, ferrochelatase (also known as heme synthetase or protoheme ferrolyase).

Question 17

Which of the following hepatic porphyrias present during adult life ?

A	Acute intermittent porphyria (AIP)
B	Hereditary coproporphyria (HCP)
C	Variegate porphyria (VP)
D	All of the above

Question 17 Explanation:

Four of the five hepatic porphyrias - acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), variegate porphyria (VP), and ALA-dehydratase porphyria (ADP) present during adult life with acute attacks of neurologic manifestations and elevated levels of one or both of the porphyrin precursors, ALA and PBG, and are thus classified as acute porphyrias. Patients with ADP have also presented in infancy and adolescence.

Question 18

Which of the following hepatic porphyrias have cutaneous manifestations ?

A	Porphyria cutanea tarda (PCT)
B	Hereditary coproporphyria (HCP)
C	Variegate porphyria (VP)
D	All of the above

Question 18 Explanation:

The fifth hepatic disorder, porphyria cutanea tarda (PCT), presents with blistering skin lesions. HCP and VP also may have cutaneous manifestations similar to PCT.

Question 19

Which of the following erythropoietic porphyrias present with cutaneous photosensitivity ?

A	Congenital erythropoietic porphyria (CEP)
B	Erythropoietic protoporphyria (EPP)
C	X-linked protoporphyria (XLP)
D	All of the above

Question 19 Explanation:

The erythropoietic porphyrias - congenital erythropoietic porphyria (CEP) & erythropoietic protoporphyria (EPP), including the recently described X-linked form, XLP are characterized by elevations of porphyrins in bone marrow and erythrocytes and present with cutaneous photosensitivity.

Question 20

A substantial increase in PBG is seen in ?

A	AIP
B	HCP
C	VP
D	All of the above

Question 20 Explanation:

A substantial increase in PBG may be due to AIP, HCP, or VP.

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See all quizzes of Porphyrias at here:

1 Which of the following is a sporadic metabolic disorder ?
A. Porphyria cutanea tarda (PCT)
B. Acute intermittent porphyria (AIP)
C. Hereditary coproporphyria (HCP)
D. Variegate porphyria (VP)

2 The most common porphyria is ?
A. Porphyria cutanea tarda (PCT)
B. Acute intermittent porphyria (AIP)
C. Hereditary coproporphyria (HCP)
D. Variegate porphyria (VP)

3 Major manifestation of the acute hepatic porphyrias is ?
A. Gastrointestinal
B. Skin
C. Neurologic
D. Endocrinal

4 Erythropoietic porphyrias usually present with ?
A. Gastrointestinal manifestations
B. Skin manifestations
C. Neurologic manifestations
D. Endocrinal manifestations

5 Heme biosynthesis involves how many enzymatic steps in the
conversion of glycine & succinyl-CoA to heme ?
A. 2
B. 4
C. 6
D. 8

6 Enzymes involved in heme biosynthesis are encoded by how
many genes ?
A. 4
B. 7
C. 9
D. 12

7 The first enzyme in the heme biosynthesis pathway is ?
A. 5’-aminolevulinate synthase (ALA-synthase)
B. 5’-aminolevulinate dehydratase (ALA-dehydratase)
C. Hydroxymethylbilane synthase (HMB-synthase or PBGdeaminase)
D. Uroporphyrinogen III synthase (URO-synthase)

8 Which of the following enzymes in the heme biosynthesis pathway
is located in mitochondrion ?
A. 5’-aminolevulinate synthase (ALA-synthase)
B. 5’-aminolevulinate dehydratase (ALA-dehydratase)
C. Hydroxymethylbilane synthase (HMB-synthase or PBGdeaminase)
D. Uroporphyrinogen III synthase (URO-synthase)

9 Heme is required for synthesis of which of the following ?
A. Hemoglobin
B. Myoglobin
C. Cytochrome P450 enzymes (CYPs)
D. All of the above

10 To confirm the diagnosis of porphyria, laboratory measurement
of porphyrin precursors is done in which of the following ?
A. Urine
B. Plasma
C. Feces
D. All of the above

11 Which of the following is involved in the formation of ALA ?
A. Glycine
B. Pyridoxal phosphate
C. Succinyl coenzyme A
D. All of the above

12 Which of the following enzymes catalyzes the condensation of
two molecules of ALA to form PBG ?
A. 5’-aminolevulinate synthase (ALA-synthase)
B. 5’-aminolevulinate dehydratase (ALA-dehydratase)
C. Hydroxymethylbilane synthase (HMB-synthase or PBGdeaminase)
D. Uroporphyrinogen III synthase (URO-synthase)

13 Head-to-tail condensation of how many PBG molecules forms
HMB ?
A. 1
B. 2
C. 3
D. 4

14 Which of the following enters mitochondrion via transporter
ABCB6 ?
A. Porphobilinogen (PBG)
B. Uroporphyrinogen (URO’gen) III
C. Coproporphyrinogen (COPRO’gen) III
D. Protoporphyrinogen (PROTO’gen) IX

15 PROTO-oxidase oxidizes PROTO IX’gen to protoporphyrin IX
by the removal of ?
A. Acetic acid side chains
B. Propionic acid groups
C. Hydrogen atoms
D. Ferrous iron atoms

16 Ferrochelatase is also called ?
A. Heme decarboxylase
B. Heme synthase
C. Protoheme synthase
D. Protoheme ferrolyase

17 Which of the following hepatic porphyrias present during adult
life ?
A. Acute intermittent porphyria (AIP)
B. Hereditary coproporphyria (HCP)
C. Variegate porphyria (VP)
D. All of the above

18 Which of the following hepatic porphyrias have cutaneous
manifestations ?

A. Porphyria cutanea tarda (PCT)
B. Hereditary coproporphyria (HCP)
C. Variegate porphyria (VP)
D. All of the above

19 Which of the following erythropoietic porphyrias present with
cutaneous photosensitivity ?
A. Congenital erythropoietic porphyria (CEP)
B. Erythropoietic protoporphyria (EPP)
C. X-linked protoporphyria (XLP)
D. All of the above

20 A substantial increase in PBG is seen in ?
A. AIP
B. HCP
C. VP
D. All of the above

Porphyrias

[MCQ] Porphyrias-Part 1

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Porphyrias-Part 1

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