Multiple Choice Question on Heme synthesis & Related Inherited Disease (Porphyria)
In this page, we will review the multiple-choice practice questions on heme synthesis and related inherited disorders including hepatic and erythropoietic porphyria. The biological importance of heme, heme biosynthesis, regulation of heme synthesis, diagnosis, and treatment of porphyria are discussed elsewhere and a link for the page is provided below.
Please review the topics by clicking the link provided below:
Multiple Choice Question on Heme synthesis
1) Heme is a tetrapyrrole structure consisting of iron (Fe+2 ions) in the center of the porphyrin ring.
Which of the following proteins consist of heme?
a) Myoglobin
b) Hemoglobin
c) Cytochrome
d) All of the above
2) Besides erythroid precursor cells, which of the following is the site for the synthesis of heme?
a) Kidney
b) Spleen
c) Liver
d) Heart
3) Which of the following is not the precursor for the synthesis of Heme?
a) Glycine
b) Succinyl CoA
c) Both of the above
d) None of the above
4) Which of the following is the rate-limiting enzyme (key enzyme) for the synthesis of heme?
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
5) The synthesis of heme involves both cytosolic and mitochondrial cellular compartments.
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
5) The synthesis of heme involves both cytosolic and mitochondrial cellular compartments.
Which of the following enzyme-catalyzed reaction occurs in the cytosol?
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
6) Lead positioning causes the increase in the accumulation and urinary excretion of coproporphyrin III and ALA in the urine.
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
6) Lead positioning causes the increase in the accumulation and urinary excretion of coproporphyrin III and ALA in the urine.
Which of the following enzymes are inhibited by lead metal?
a) ALA synthase and Protoporphyrin oxidase
b) ALA synthase and Ferrochelatase
c) ALA dehydratase and Protoporphyrin oxidase
d) ALA dehydratase and Ferrochelatase
7) The heme, hematin, and Cytochrome P450 represses the synthesis of the following enzyme thereby reducing heme synthesis.
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
8) Which of the following intermediate of the heme synthetic pathway is water-insoluble and excreted via feces via the biliary tract?
a) delta-aminolevulinic acid
b) Porphobilinogen
c) Uroporphyrinogen
d) Protoporphyrin
9) Porphyria refers to a group of metabolic disorders or rare genetic disorders that result from partial deficiencies of the enzyme and abnormalities in the heme biosynthetic pathway. The porphyria may be classified as acute and nonacute.
a) ALA synthase and Protoporphyrin oxidase
b) ALA synthase and Ferrochelatase
c) ALA dehydratase and Protoporphyrin oxidase
d) ALA dehydratase and Ferrochelatase
7) The heme, hematin, and Cytochrome P450 represses the synthesis of the following enzyme thereby reducing heme synthesis.
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
8) Which of the following intermediate of the heme synthetic pathway is water-insoluble and excreted via feces via the biliary tract?
a) delta-aminolevulinic acid
b) Porphobilinogen
c) Uroporphyrinogen
d) Protoporphyrin
9) Porphyria refers to a group of metabolic disorders or rare genetic disorders that result from partial deficiencies of the enzyme and abnormalities in the heme biosynthetic pathway. The porphyria may be classified as acute and nonacute.
Which of the following porphyria is not acute type?
a) Acute intermittent porphyria
b) Hereditary coproporphyria
c) Variegate porphyria
d) Porphyria cutanea tarda (PCT)
10) Identify porphyria that does not have accumulation and increased excretion of delta-aminolevulinic acid and porphobilinogen among the following:
a) Acute intermittent porphyria (AIP)
b) Hereditary coproporphyria (HCP)
c) Congenital erythropoietic porphyria (CEP)
d) Variegate porphyria (VP)
11) Porphyria Cutanea tarda (PCT) is the most common porphyria characterized by photosensitivity and skin lesions.
a) Acute intermittent porphyria
b) Hereditary coproporphyria
c) Variegate porphyria
d) Porphyria cutanea tarda (PCT)
10) Identify porphyria that does not have accumulation and increased excretion of delta-aminolevulinic acid and porphobilinogen among the following:
a) Acute intermittent porphyria (AIP)
b) Hereditary coproporphyria (HCP)
c) Congenital erythropoietic porphyria (CEP)
d) Variegate porphyria (VP)
11) Porphyria Cutanea tarda (PCT) is the most common porphyria characterized by photosensitivity and skin lesions.
Which of the following statement is false regarding PCT?
a) PCT is caused by the deficiency of uroporphyrinogen decarboxylase enzyme
b) Accumulation of photo-sensitizers such as uroporphyrinogen and carboxyl-substituted porphyrinogen
c) Accumulation of ALA (delta-aminolevulinic acid) and PBG (porphobilinogen)
d) None of the above
12) Which of the following is the most sensitive method for the measurement of porphobilinogen?
a) Colorimetric Ehrlich's reaction method
d) Ion exchange chromatography-based method
c) HPLC coupled MS
d) Spectral analysis of porphobilinogen
13) All types of porphyria are inherited in an autosomal dominant fashion except for the following two autosomal recessive conditions
a) ALA synthase deficiency
b) ALA dehydratase deficiency
c) Congenital erythropoietic porphyria
d) Hereditary coproporphyria
14) The enzyme deficient in erythropoietic protoporphyria (EPP) is............................................
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
15) The intravenous administration of hemin is required for reducing symptoms during acute porphyria attacks.
a) PCT is caused by the deficiency of uroporphyrinogen decarboxylase enzyme
b) Accumulation of photo-sensitizers such as uroporphyrinogen and carboxyl-substituted porphyrinogen
c) Accumulation of ALA (delta-aminolevulinic acid) and PBG (porphobilinogen)
d) None of the above
12) Which of the following is the most sensitive method for the measurement of porphobilinogen?
a) Colorimetric Ehrlich's reaction method
d) Ion exchange chromatography-based method
c) HPLC coupled MS
d) Spectral analysis of porphobilinogen
13) All types of porphyria are inherited in an autosomal dominant fashion except for the following two autosomal recessive conditions
a) ALA synthase deficiency
b) ALA dehydratase deficiency
c) Congenital erythropoietic porphyria
d) Hereditary coproporphyria
14) The enzyme deficient in erythropoietic protoporphyria (EPP) is............................................
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
15) The intravenous administration of hemin is required for reducing symptoms during acute porphyria attacks.
The hemin decreases the gene synthesis of which of the following enzyme?
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
a) delta-aminolevulinic acid synthase 1
b) Uroporphyrinogen synthase III
c) Protoporphyrinogen oxidase
d) Ferrochelatase
Answers with explanation:
1-d) All of the above. a) Myoglobin is a protein found in striated muscles (skeletal muscles and heart muscles), b) Hemoglobin is the iron containing protein in red blood cells (RBCs) and c) Cytochrome is a heme protein involved in electron transport chain.
1-d) All of the above. a) Myoglobin is a protein found in striated muscles (skeletal muscles and heart muscles), b) Hemoglobin is the iron containing protein in red blood cells (RBCs) and c) Cytochrome is a heme protein involved in electron transport chain.
2-c) Liver, the heme synthesis occurs for the cytochrome P450 in the liver.
3-d) None of the above
4-a) delta-aminolevulinic acid synthase, the enzyme of the initial step of the heme synthesis pathway.
5- b) Uroporphyrinogen synthase III produce uroporphyrinogen III (UPG III). The synthesis of heme occurs in several steps within cells, mainly in the mitochondria and cytoplasm.
6-d) ALA dehydratase and Ferrochelatase
7- a) delta-aminolevulinic acid synthase 1
8-d) Protoporphyrin
9-d) Porphyria cutanea tarda (PCT), it is the most common form of porphyria overall. It results from reduced activity of the enzyme uroporphyrinogen decarboxylase. Primarily affects the skin, leading to photosensitivity, blistering, scarring, and increased hair growth. It may also be associated with liver abnormalities and can be triggered by certain medications, alcohol, and iron overload.
10- c) Congenital erythropoietic porphyria (CEP), is a rare autosomal recessive disorder caused by a deficiency of the enzyme uroporphyrinogen III synthase. It leads to the accumulation of porphyrins in the bone marrow, blood, and skin. Symptoms include extreme photosensitivity, skin fragility, hemolytic anemia, and bone abnormalities.
11-c) Accumulation of ALA (delta-aminolevulinic acid) and PBG (porphobilinogen)
12 -c) HPLC coupled MS
13- b) ALA dehydratase deficiency & c) Congenital erythropoietic porphyria
14-d) Ferrochelatase, deficiency of ferrochelatase leads to the buildup of protoporphyrin IX.
15-a) delta-aminolevulinic acid synthase 1, the enzyme involved in the initial step in the heme synthesis pathway.
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| Heme Synthesis (Porphyrin synthesis) pathway & Porphyria (Diagram NEMJ) |
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