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Biochemistry > Heme Synthesis > Flashcards

Heme Synthesis Flashcards

1
Q

4 pyrrole rings

A

Porphyrins

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2
Q

Porphyrins + metal ions

A

Metalloporphyrins

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3
Q

Reduced porphyrins

A

Phorphorynogen

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4
Q

Heme + proteins

A

Hemoproteins

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5
Q

Biosynthesis of heme ring occurs in the

A

mitochondria and cytosol

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6
Q

Heme is synthesized from

A

Succinyl CoA

Glycine

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7
Q

Examples of hemoproteins

A

Hemoglobin CYP450
Myoglobin catalase
Cytochrome c Tryptophan pyrrolase

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8
Q

Needed to activate glycine

A

Pyridoxal phosphate

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9
Q

Rate limiting step in Heme Synthesis

A

ALA Synthase

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10
Q

Occurs in all cells due to the requirement for heme as a prosthetic

Group of enzymes and electron transport chain proteins

A

Heme Synthesis

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11
Q

Major locations of heme synthesis

A

Liver (CYP450)

Erythroid progenitor cells (hemoglobin)

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12
Q

Integral or Intrinsic Proteins

A

Band 3

Glycophorin

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13
Q

Peripheral or Extrinsic Proteins

A

Spectrin
Actin
Protein 4.1

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14
Q

Two forms of Quarternary Structure of Hemoglobin

A

R (relaxed) form

T (taut) form

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15
Q

Binds oxygen several hundred times more readily than T form

Increase in this form shifts the curve to the left

A

R relaxed form

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16
Q

Ends of b chains form salt bridges stabilizing it

Reduced affinity for oxygen

Inc in this form shifts the curve to the right

Ex

A

T (tense) form

Chlorophyll
Heme of hemoglobin

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17
Q

Inc acidity

Dec pH

A

Shift to the right

Bohr effect

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18
Q

Inc Partial pressure of CO2

HCO3 leaves the RBCs into plasma

A

Shift to the right

Bohr effect

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19
Q

When HCO3 leaves the RBCs into the plasma and HCO3 is replaced by Cl

A

Chloride shift

20
Q

Inc in temperature

A

Shift to the right

Bohr effect

21
Q

Hypothermia

A

Shift to the left

Haldane

22
Q

Inc 2,3 DPG

A

Shift to the right
Bohr effect

One DPG molecule binds to each Hb and stabilizes T form promoting O2 release

23
Q

Has affinity for Hb 200x that of oxygen

Once bound, does not dissociate

A

Carbon monoxide

24
Q

Binds only to methemoglobin
Prevents reduction to active form
Impairs ability of blood to transport O2

A

Cyanide

25
Q

Genetic disorders of heme metabolism

Can also be acquired by intake of

A

Porphyrins

Lead

26
Q

6 major types
Classified on the basis of the organs or cells that are most affected

Major sites are RBC and liver

Photosensitivity and neurologic problems

A

Pophyria

27
Q

Photosensitivity (blistering of skin when exposed to sunlight)
Hypertrichosis
Oncholysis
Most common subtype of porphyria
Named because it is a porphyria that presents with skin manifestations later in life

A

Porphyria cutaneous tarda

28
Q

Porphyria cutaneous tarda is a problem with this enzyme

A

Uroporphyrinogen decarboxylase (UROD)

29
Q

Abdominal pain

Neuropsychiatric symptoms

A

Acute intermittent porphyria

30
Q

Acute intermittent porphyria is caused by deficiency of this enzyme

A

Uroporphyrinogen I synthase

31
Q

During fasting, lactate from RBC and exercising muscle is converted in the liver to glucose that is returned to RBC and muscle

A

Cori Cycle

32
Q

Muscle releases alanine delivering both gluconeogenic subtrate and an amino group for urea synthesis

A

Alanine cycle

33
Q

Porphyria tx

A

Avoid drugs that cause induction of CYP450
Photosensitivity administer beta carotene
Sunscreen

34
Q

How many erythrocytes are destroyed in 1 day

A

200B

35
Q

70kg human daily turnover of heme

A

6g hemoglobin

36
Q

Globin is degraded into

A

Amino acids and reused

37
Q

Iron during heme catabolism

A

Goes back to iron pool

38
Q

Porphyrin goes to the

A

Reticuloendothelial cells (liver, spleen, bone marrow)

39
Q

Enzyme that catalyzes breakdown of heme

A

Heme oxygenase

40
Q

End product of heme metabolism

A

Bilirubin

41
Q

1g hemoglobin yields

A

35 mg bilirubin

42
Q

Daily bilirubin formation

A

250-350 mg

43
Q

Early product of catabolism and on reduction yields bilirubin

A

Biliverdin

44
Q

Formed in peripheral tissues

Transported to liver by plasma albumin

A

Bilirubin

45
Q

How is bilirubin metabolized

A

Uptake of bilirubin by liver parenchymal cells
Conjugation of bilirubin with glucoronate in the ER
Secretion of conjugated bilirubin

Biochemistry (32 decks)

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