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Biochemistry > Heme Metabolism > Flashcards

Heme Metabolism Flashcards

1
Q

Cyclic compounds formed by the linkage of 4 pyrrole rings through methyne or methenyl bridges

A

PORPHYRINS

IRON PORPHYRINS - Heme of Hemoglobin

MAGNESIUM CONTAINING PORPHYRIN -
CHLOROPHYLL

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2
Q

3 important porphyrins

A

UROPORPHYRIN
COPROPORPHYRIN
PROTOPORPHYRIN

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3
Q

Iron in the heme is in

A

FERROUS STATE

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4
Q

TRANSPORT of Oxygen in Blood

A

HEMOGLOBIN

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5
Q

STORAGE of Oxygen in Blood

A

MYOGLOBIN

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6
Q

Involvement in ETC

A

Cytochrome C

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7
Q

Hydroxylation of xenobiotics

A

Cytochrome P450

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8
Q

Degradation of hydrogen peroxide

A

CATALASE

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9
Q

Oxidation of Tryptophan

A

TRYPTOPHAN PYRROLASE

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10
Q

Site of Heme Synthesis

A

all tissues EXCEPT mature erythrocytes

cytoplasm and mitochondria

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11
Q

Substrates of Heme Synthesis

A

Succinyl CoA and Glycine

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12
Q

Rare limiting step of Heme Synthesis

A

glycine + succinyl CoA –> delta aminolevulinic acid (ALA)

ALA SYNTHASE
Pyridoxine - cofactor

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13
Q

Isoform of ALAS expressed throughout the BODY

A

ALAS I
rate limiting step
HEME - (-) regulator if ALAS I
induced by drugs whose metabolism requires cytochromes

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14
Q

Isoform of ALAS expressed in erythrocyte precursor cells

A

ALAS II
not feedback regulated by heme
not induced by drugs

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15
Q

Formation of Porphobilinogen

A

ALA DEHYDRATASE - condenses 2 molecules of ALA

(-) by heavy metal ions that replace the zinc

cytosol

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16
Q

The first porphyrin precursor formed

A

UROPORPHYRINOGEN

17
Q

Enzyme most sensitive to lead poisoning

A

ALA DEHYDRATASE

18
Q

LEAD POISONING

lead inactivates many enzymes in heme synthesis

A

INCREASED urinary ALA and free erythrocyte porphyrins

microcytic, hypochromic ANEMIA

headache, memory loss

peripheral NEUROPATHY, claw hand, wrist drop

nausea, abdominal pain, diarrhea

lead lines in gums

lead deposits EPIPHYSES

19
Q

The final step in heme synthesis

A

Formation of Heme by Incorporation of Iron

FERROCHELATASE (HEME SYNTHASE)

MITOCHONDRIA

20
Q

Group of disorders d.t. abnormalities in the pathway of biosynthesis of heme

A

Porphyrias

photosensitivity
neuropsychiatric symptoms
abdominal pain

21
Q

MC porphyria

A

Prophyria Cutanea Tarda (PCT)

photosensitivity
urine that is red to brown in natural light d.t. uroporphyrins

22
Q

MC acute porphyria

A

Acute Intermittent Porphyria

abdominal pain
neuropsychiatric symptoms d.t. ALA and PBG accumulation

23
Q

MC porphyria in children

A

Erythropoietic Protoporphyria (EPP)

24
Q

Porphyria that is frequently seen in countries where Hepa C and HIV is prevalent

A

Pophyria Cutanea Tarda

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