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IHL Exam 1 Me > Hemoglobin Synthesis and Catabolism (McCormick) > Flashcards

Hemoglobin Synthesis and Catabolism (McCormick) Flashcards

2
Q

2 main components of hemoglobin

A

hemeglobin proteins. 2 pair chains

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3
Q

heme structure

A

have 4 N bonds to attach to Fe. Porphyrin ring.4 hemes per molecule

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4
Q

what are the two distinct globin chains in hemoglobin

A

alpha and non-alpha(because can be many different types)

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5
Q

rate limiting step of heme synthesis

A

ALA synthaseglycine + aminolevulinic acid

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6
Q

Steps of heme synthesis and where do they take place

A

1) form porphobilinogen via ALA synthase(mitochondria) and PBG synthase (cytosol)2) form heme from protoporphyrin ring and Fe (mitochondria)

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7
Q

Formation of protoporphyrin ring?

A

condensation of 4 PBG in cytosol

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8
Q

Where does Fe join with heme?

A

in the mitichondria

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9
Q

Mutation of ALA synthase?

A

Sideroblastic anemia, no heme to insert Fe into. so Fe accumulates and precipitates in granules outside RBC (demonstrate ringed sideroblasts)

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10
Q

What mutations cause porphyria and what are symptoms?

A

ALA dehydrase and PBG synthaseaccumulation of substrate on skin- extremely photosensitive. Urine is red

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11
Q

Pb poising inhibits what enzymes

A

ALA dehydrase and ferochelataseaccumulation of productscauses basophilic stipling (see lots of purple dots b/c accumulation of products)

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12
Q

Where does globin synthesis take place

A

cytoplasm of normoblasts and reticulocytes(immature RBC)

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13
Q

What stimulates globin synthesis

A

increase of heme availability

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14
Q

where are alpha chains gene located

A

chromosome 16

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15
Q

where are beta chains gene located

A

chromosome 11

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16
Q

thalassemia

A

unbalanced gene expression of the globin chains for hemoglobin

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17
Q

What is required for the combination of heme and globin

A
  1. adequate supply of Fe. 2. Normal Heme synthesis, leaves mitochondria.join in cytoplasm.3. Normal globin synthesis (in cytoplasmic ribosomes) Hb in adult have two alpha, two beta
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18
Q

HbF

A

2 alpha and 2 gamma

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19
Q

Hb A2

A

2 alpha and 2 delta.

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20
Q

During gestation what Hb are most common

A

alpha chain, and gamma chaingower chain lasts till about 3 mo

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21
Q

Describe Hb production at birth

A

gamma chain drops rapidly for 6 months and Beta chain increases rapidly for 6 monthsdelta slowly slowly increases

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22
Q

Deoxyhemoglobin

A

reduced hemoglobin. not carrying O2

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23
Q

Oxyhemoglobin

A

hemoglobin carrying O2, can be measured by pulse oximetry

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24
Q

Red pulse oximetry

A

deoxyHb and OxyHb absorb light at different wavelengths, we can measure the difference and compute how much oxygen you have on board (your saturation)

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25
Q

MetHb

A

hemoglobin carrying ferric iron (Fe3+) loses ability to bind O2 (usually less than 3% of total hgb)usually caused by oxidizing drugs (nitrites or sulfonamides)

26
Q

Methemoglobin reductase

A

convert metHb back to Hb. This is a protective enzyme of RBC’s

27
Q

Sulhemoglobin

A

oxidized partially denatured Hb–> may result in RBC destruction and hemolysiscannot carry O2this is not usually present!formed from sulfur-containing drugs or aromatic amine drugs

28
Q

CarboxyHb

A

carrying CO produced during heme degradation to bilirubin elevated levels of CarboxyHb in people with CO poisoning.

29
Q

Fe2+ bonds in functional hemoglobin

A

four to attach to heme, one attaches to globin chain and one binds (reversibly) to O2

30
Q

Where is the Fe to be inserted into heme coming from ?

A

primarily diet.we have heme and nonheme

31
Q

non heme Fe

A

from diet primarily. Ferrous form absorbed most readily, so Fe3+ must be reduced by ferric reductase. Dcytb.DMT1 cotransports Fe2+ and H+in cell, minds mobilferrin (ferroportin) to be transported

32
Q

Ferroportin (aka mobilferrin)

A

basolateral membrane protein that binds Fe2+ and and allows the Fe2+ to enter the bloodexpressed by a gene, regulated by hepcidin

33
Q

hemachromatosis

A

iron overload. can give the pt’s chelating proteins to bind Fe and prevent the overload

34
Q

Heme iron

A

from breakdown of meats and RBCs in body. absorbed by duodenal epithelium via binding or endocytosis.Intracell: heme oxygenase splits heme and releases free Fe3+

35
Q

how is Fe3+ converted to Fe2+ for heme iron

A

enterocytes

36
Q

How do we store Fe

A

In spleen and liver, absorbed in duodenum.apoferritin takes up Fe for storage

37
Q

RBC destruction

A

120 days in circulation. then called senescent RBCs, spleen takes them out of circulation (2-3 million cells per day)

38
Q

Where does RBC get energy

A

without mitochondria they use glycolysis and pentose phosphate cycle (HMP shunt)

39
Q

how does spleen get rid of RBC

A

phagocytosis in specific macrophages found in spleen sinusoids

40
Q

polycythemia

A

RBC synthesis is greater than destruction

41
Q

anemia

A

RBC destruction greater than synthesis

42
Q

Hemoglobinemia (plasma) of hemoglobinuria (urine)

A

intravascular hemolysis of RBCs form hemolytic anemia, autoimmune processes, transfusion reactions. This causes free Hb in plasma and urineleading to nephrotoxicity (which is damaging to the kidneys)

43
Q

Hb desctruction

A

macrophages in RES system degrade hemoglobin into 3 components:1) Fe (goes to storage for reutilization)2) Protoporphyrin (converted to bilirubin)3) Globin (converted to aa’s, recycled)

44
Q

what does protoporphyrin get recycled as

A

biliverdin –> bilirubin

45
Q

HbS

A

at position 6, glutamic acid has been replaced by valine due to missense mutation of Beta globin chainresults in production of HbSHeterozygous vs. Homozygous At six months Hgb S replaces Hgb F (instead of Hgb A replacing Hgb F, which normally happens at six months)

46
Q

Thalassemia : quantitative defect

A

quantitative defect, not enough producedheterozygote resistance to malaria

47
Q

microcytic hypochromic anemia

A

underproduced globin chainsmicrocytic (small cell) hypochromic (does not stain as dark “ghost cells”prominent target cells on peripheral smear (looks just like a bullseye) Decrease in MCV (mean corpuscular volume) and MCH (mean corpuscular hemoglobin, or amount of hemoglobin per cell)hemoglobin A is usually decreased

48
Q

alpha thalassemia? give examples (x2)

A

overabundance of beta or gamma chainExamples:Hb H disease (lose 3 of the 4 alpha genes) results in beta tetramersThalassemia major (lose all 4 alpha genes producing tetramer of gamma globin- results in hydrops fetalis with hepatosplenomegaly - die in uterothis type of hemoglobin can’t carry oxygen so die of anoxia

49
Q

Beta thalassemia? give examples

A

excess of alpha chains. or elevated HbF or A2B- thalassemia minor- heterozygous disorderB-thalassemia major- homozygous disorider, resulting in cooley’s anemia.show target cells on smear. overabundance of membrane for the amount of hemoglobin and cells collapse on themselves, so can only see hemoglobin on inside and outside of cell. (bullseye)

50
Q

Beta thalassemia signs

A

producing so much RBCs, cause expansion of marrow spaces–> pushes out bones.”hair-on-end” on skull radiograph (looks like hair)note–> B-thalaseemia is endemic in certain populations throughout europe and africa

51
Q

ALA synthase

A

located in the mitochondria takes succinyl CoA + glycine and makes ALA(condensation rxn)Rate limiting enzymeinhibiting by heme feedback system, which represses transcription of the gene for ALA synthase

52
Q

PBG synthase

A

also known as ALA Dehydrataselocated in the cytosolcatalyzes condensation of two molecules of ALA to form PBG (porphobilinogen)

53
Q

Ferrochelatase

A

inserts iron into protoporphyrin in the mitochondria to form heme

54
Q

As oxygen partial pressure increases…

A

each of the four heme groups binds one molecule of oxygen (more ability of the hemoglobin to bind oxygen)

55
Q

hepcidin

A

controls expression of ferroportinif hepcidin attaches to ferroportin causes it to disintegrate and internalize into the cellregulates iron absorption by decreasing absorption of iron by intestine

56
Q

heme oxygenase

A

splits heme iron into free Fe3+this is located inside the epithelium cell

57
Q

appoferritin

A

storage protein in RES that is the iron buffer systemhelps convert iron from transferrin the plasma to ferritin (storage form of iron)

58
Q

heme oxygenase (oxidase)

A

located in the macrophage of RES breaks down porphyrin ring to CO and biliverdin

59
Q

Sickle Cell Disease

A

HgSthis disease causes hemoglobin to be susceptible to polymerization at low oxygen concentrations Reduces flexibility of RBC membrane”sickling” of RBC’s resultsthese sickled cells can’t get through capillaries and causes “crises or occlusions” resulting in hypoxic tissue injury

60
Q

Symptoms of Cooley’s anemia

A

HepatosplenomegalyProminent protruding forehead and flattened nose b/c pt does not have enough oxygen carrying ability so the body thinks it is starving for oxygen so it produces more RBC’sRBC’s are overproduced which expand the marrow spaces in bone “hair on end” due to new bone formation

IHL Exam 1 Me (11 decks)

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