Heme and Iron

In heme synthesis in mammalian cells:

1. Succinyl CoA and alanine are the immediate substrates for formation of d-aminolevulinic acid
2. Ferric iron is inserted into protoporphyrin IX
3. Coproporphyrin IV is an intermediate
4. Porphobilinogen is formed by the condensation of two molecules of d-aminolevulinic acid

Protoporphyrin IX:

A. Intermediate in heme synthesis

B. Intermediate in heme degradation

1. A only
2. B only
3. Both A and B
4. Neither A or B

Coproporphyrinogen I:

A. Intermediate in heme synthesis

B. Intermediate in heme degradation

1. A only
2. B only
3. Both A and B
4. Neither A or B

A patient with blockage of hepatic biliary network:

A. Increased "Indirect" bilirubin in blood

B. Increased "Direct" bilirubin in blood

1. A only
2. B only
3. Both A and B
4. Neither A or B

A patient with decreased hepatic uptake of bilirubin:

A. Increased "Indirect" bilirubin in blood

B. Increased "Direct" bilirubin in blood

1. A only
2. B only
3. Both A and B
4. Neither A or B

In hereditary protoporphyria, which enzyme of heme synthesis is decreased?

1. Coproporphyrinogen oxidase
2. Ferrochelatase
3. Porphobilinogen synthase
4. Uroporphyrinogen oxidase
5. Uroporphyrinogen synthase

Porphobilinogen synthase (d-aminolevulinic acid dehydratase):

A. Is the control step in heme synthesis

B. Is inhibited by lead

C. Requires pyridoxal (vitamin B6) phosphate for activity

D. Is present in the cytosol

1. A, B, and C
2. A and C
3. B and D
4. D only
5. All of the above

Contain(s) propionic acid and acetic acid side chains on pyrrole rings:

A. Uroporphyrinogen I

B. Uroporphyrin III

1. A only
2. B only
3. Both A and B
4. Neither A or B

Formed directly by the condensation of porphobilinogens:

A. Uroporphyrinogen I

B. Uroporphyrin III

1. A only
2. B only
3. Both A and B
4. Neither A or B

In heme synthesis in mammalian cells:

A. Uroporphyrin III is the immediate precursor of coproporphyrin III

B. d-Aminolevulinic acid is formed by the condensation of succinyl CoA and valine

C. Ferric iron is inserted into protoporphyrin IX prior to attachment to the globin molecule

D. Porphobilinogen is formed by the condensation of two d-aminolevulinic acids

1. A, B, and C
2. A and C
3. B and D
4. D only
5. All of the above

A rise in serum "direct" bilirubin would be expected in:

A. Hemolytic jaundice

B. Absence of glucuronyl tranferase as in the newborn

C. Decreased hepatic uptake of bilirubin (Gilbert's Disease)

D. Biliary obstruction

1. A, B, and C
2. A and C
3. B and D
4. D only
5. All of the above

In iron metabolism:

A. Iron stored in liver cells is transported across cell membranes in the ferrous state

B. The major plasma transport protein for iron is hemosiderin

C. In the form of ferritin, iron may accumulate in mucosal cells of the duodenum

D. Nearly all iron in the diet is absorbed and any excess secreted in the feces

1. A, B, and C
2. A and C
3. B and D
4. D only
5. All of the above

d-Aminolevulinic acid synthase:

A. Requires pyridoxal phosphate for acivity

B. Synthesis can be induced by phenobarbital and some steroids

C. Is inhibited by heme

D. Is inhibited by lead

1. A, B, and C
2. A and C
3. B and D
4. D only
5. All of the above

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