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MSS-IHL Exam 1 > IHL I - Hemoglobin Synthesis and Metabolism > Flashcards

IHL I - Hemoglobin Synthesis and Metabolism Flashcards

0
Q

structure of heme

A

porphyrin ring with one iron chelated in the center by 4 nitrogens

iron has 6 binding sites

- 4 nitrogen
- 1 to protein structure
- 1 to oxygen
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1
Q

two major components of hemoglobin

A

heme and blogin

heme 3%

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2
Q

how many hemes per hemoglobin?

A

4 hemes (4 irons) each can carry 4 oxygen

16 O2 molecules per hemoglobin

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3
Q

porphobilinogen

A

first step in heme synthesis

-succinyl CoA and glycine decarboxylation eventually give porphobilinigen

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4
Q

delta-aminolevulinate synthase (ALA synthase)

A

committed step of heme synthesis
catalyzed reaction:
glycine and succinyl CoA > delta-aminolevulinic acid

(-) Heme - represses transcription of the enzyme

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5
Q

PBG Synthase (porphobilinogen synthase)

A

aka ALA dehydratase

catalyzes reaction:
2x delta-aminolevulinic acid > porphobilniogen

occurs in the mitochondria

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6
Q

protoporphyrin

A

condensation of four porphobilinogen > protoporphyrin

forms in the cytosol

iron is inserted into protoporphyrin by ferrochelatase

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7
Q

ferrochelotase

A

inserts the iron into the protoporphyrin ring

occurs in the mitochondria

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8
Q

sideroblastic anemia

A

due to mutation in the delta-aminolevulinic acid synthase (ALA synthase)

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9
Q

porphyria

A

due to mutations in ALA dehydratase or PBG deaminase

- results in accumulation of these in the skin
- very photosensitive
- red-colored urine
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10
Q

lead poisoning

A

inhibits ALA dehydratase and ferrochelatase

accumulation of molecules

- causes basophilic stiffling
	- little purple dots in the RBCs
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11
Q

globin synthesis

A

in the cytoplasm of immature RBCs

somehow there is a balance of heme and globin
-unknown mechanism

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12
Q

chromosome 16

A

alpha chains of globin

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13
Q

chromosome 11

A

beta globin chains, as well as delta and gamma

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14
Q

thalassemia

A

disruption of balance in the globin and heme synthesis

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15
Q

hemoglobin synthesis

A

combination of heme and globin in the immature RBCs in bone marrow

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16
Q

transferrin

A

transports iron in the body

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17
Q

location on heme synthesis

A

mitochondria

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18
Q

location of globin synthesis

A

cytoplasm ribosomes

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19
Q

Hb A

A

normal adult hemoglobin

2 alpha and 2 beta chains

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20
Q

variation in hemoglobin?

A

heme all the same

globin chains can be different

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21
Q

Hb F

A

2 alpha and 2 gamma

fetal hemoglobin

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22
Q

Hb A2

A

2 alpha and 2 delta

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23
Q

hemoglobin through development?

A 
conception to 3 months
	-have Gower hemoglobin (e and zeta)
		-not in adult
at 3 months until birth
	-Hb F forms (gamma chain production)
		-doesn't let oxygen go easily
at birth - beta chain is synthesized
	-Hb A1 (normal adult hemoglobin) > around 6 months
increased in delta chain is slight throughout life
	-increases Hb A2
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24
Q

deoxyhemoglobin

A

without oxygen

25
Q

oxyhemoglobin

A

hemoglobin carrying oxygen

26
Q

pulse oximetry

A

infrared light measures absorption of deoxy and oxyhemoglobin
-can compute the oxygen saturation levels

27
Q

methemoglobin

A

when Fe2+ oxidized to Fe3+
-due to oxidizing drugs > nitrites, sulfonamides
cannot carry O2

28
Q

methemoglobin reductase

A

converts methemoglobin to hemoglobin

29
Q

sulfhemoglobin

A

partially denatured hemoglobin

- RBC desctruction and hemolysis
- cannot carry O2

due to sulfur drugs and aromatic amine drugs

30
Q

carboxyhemoglobin

A

hemoglobin carrying carbon monoxide

elevated in individuals with carbon monoxide poisoning

31
Q

ferrous

A

Fe2+ binds oxygen

32
Q

ferric

A

Fe3+ cannot carry O2

33
Q

major sources of iron in the body?

A

heme and nonheme

34
Q

nonheme

A

can be either ferric or ferrous

ferrous absorbed more readily
-reduced at the membrane by ferric reductase

35
Q

ferric reductase

A

reduces iron at the membrane so it can be transported

36
Q

DMT-I

A

cotransporter of Iron and H+ ions into the enterocyte

37
Q

mobilferrin

A

binds to the free iron in the enterocyte and transport to basolateral membrane

38
Q

hemochromatosis

A

too much iron

given phlebotomys and chelating agents (to bind iron)

39
Q

iron storage locations?

A

spleen, liver, duodenum

spleen - old RBCs broken down

40
Q

apoferritin

A

part of the iron buffer system

ferritin is the storage form of iron

41
Q

RBC destruction

A

circulate for 120 days > then become senescent RBCs

42
Q

erythrocyte energy production?

A

glycolysis and pentose phosphate

90% glucose in glycolysis

43
Q

glycolysis in erythrocytes

A

formation of ATP which mantains the membrane ion pumps (ATP) and reoxidation of hemoglobin (NADH)

44
Q

pentose phosphate pathway in erythrocytes

A

provides NADPH to maintain the reduced state of glutathione and sulfhydryl groups

45
Q

spleen

A

“red cell graveyard”

red blood cells lose size and become rigid as they age

46
Q

polycythemia

A

rate of RBC synthesis > degradation

47
Q

anemia

A

RBC destruction > synthesis

48
Q

hemoglobinemia

A

intravascular hemolysis of RBCs due to conditions such as hemolytic anemia, autoimmune processes, transfusion reactions, and drug-induced hemolysis

> free Hg in plasma

49
Q

hemoglobinuria

A

increased Hg in the urine

excess Hg is nephrotoxic in kidneys***

50
Q

three components of Hg breakdown

A

Fe, protoporphyrin, and globin

broken down heme oxygenase
-forms CO and biliverdin

biliverdin reduced to bilirubin

51
Q

Hemoglobin S

A

sickle cell anemia

beta chain position 6 glutamic acid changed to valine***

missense mutation > results in Hg S synthesis

52
Q

Sickle Cell Anemia

A

hemoglobin is susceptible to polymerization

- causes sickling
- results in inflexibility and hemolysis
53
Q

Thalassemias

A

quantitative defect
-imbalance in heme to globin ration

due to mutations in globin chain synthesis

54
Q

microcytic hypochromic anemia

A

small in size and decrease in color

55
Q

alpha thalassemia

A

decreased alpha globin synthesis

-results in excess of beta and gamma chains

56
Q

hemoglobin H disease

A

loss of 3 out of 4 alpha globin genes in adult

-results in Hg H (hemoglobin tetramers)

57
Q

thalassemia major

A

loss of all 4 alpha chain globin

results in formation of Hemoglobin barts (gamma tetramers)
-can cause hydrops fetalis

58
Q

hydrops fetalis

A

incompatible with life
-hepatosplenomegaly
caused by loss of all 4 alpha globin chains

59
Q

beta-thalassemia

A

excess of alpha globin chains

elevated Hg F and Hg A2

different ranges: minor > major

60
Q

beta-thalassemia minor

A

heterozygous

-asymptomatic, may require genetic counseling

61
Q

beta-thalassemia major

A

homozygous disorder

significant imbalance of alpha and beta chains
-sever anemia in early life
requires life-long RBC transfusion

untreated, death in first decade

aka cooley’s anemia

MSS-IHL Exam 1 (13 decks)

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