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MCM test 2 > Erythrocyte Biochem > Flashcards

Erythrocyte Biochem Flashcards

1
Q

Erythropoiesis

A

-starts as stem cell
• Majority of Hb synthesized before extrusion of nucleus
• Small amount made in reticulocyte

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2
Q

hemoglobin structure

A

• Multi-subunit
protein (tetramer)
– 2 a-globin chains
– 2 b-globin chains

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3
Q

heme

A 
– One per hemoglobin subunit
– Has iron atom
(ferrous : Fe2+)
– Carries O2
– Hydrophobic
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4
Q

Embryonic hemoglobin

A

Hb Gower 1 (]2epislon2)
Hb Gower 2 (a2epsilon2)
Hb Portland (]2gmma2)

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5
Q

fetal hemoglobin

A

Hb F (a2gamma2), 0.5%

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6
Q

adult hemoglobin

A 
Hb A (a2b2), 97%
Hb A2(a2G2), 3%
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7
Q

what are chains of hemoglobin derived from?

A

diff genes located on diff chromosomes (16 and 11)

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8
Q

treatment for sickle cell anemia

A

induce expression of HbF
using hydroxyurea
but this is a toxic
chemotherapeutic agent

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9
Q

what is the proximal histidine

A

The F8 histidine (bound to heme)

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10
Q

what is the distal histidine

A

The E7 histidine

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11
Q

where does O2 bind?

A 
binds to
the iron
between the
heme and distal
histidine
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12
Q

what is the conformation change when O2 binds?

A

pulls down the proximal F8 histidine of Hb and

changes interaction with associated globin chain

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13
Q

what kind of curve is myoglobin

A

hyperbolic

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14
Q

what kind of curve is hemoglobin

A

sigmoidal (due to interactions between globin subunits)

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15
Q

positive cooperativity

A
  • Binding of one molecule of O2 to one heme, facilitates the
    binding of an O2 to another heme
    -Conformational change in one globin subunit induces a
    conformational change in another subunit in Hb
  • The binding of O2 to Fe of a globin subunit pulls the proximal
    F8 histidine down
  • This pulls on the globin FG-helix and changes the interaction
    with the other globin chains in Hb
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16
Q

Bohr Effect

A

decrease in Ph causes binding affinity of Hb for O2 to decrease (right shift)
-causes release of o2

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17
Q

2,3-BPG

A
  • causes right shift

- reduces O2 affinity so Hb gives up more O2 to tissues

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18
Q

effects of o2 on ODC

A

drop in P02 from 40 to 20 torr

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19
Q

why does HbF have higher O2 affinity than HbA

A

Hbf does not bind well to 2,3 BPG therefore has higher affinity for O2

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20
Q

in what form is iron stored?

A

Fe 3+ (ferric)

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21
Q

in what form is iron transfered in blood

22
Q

how does nonheme iron enter enterocyte?

A

ferric reductase converts to Fe2+

-Fe 2+ enters enterocyte through divalent transporter-1(DMT1)

23
Q

what converts Fe 2+ to Fe 3+

A

hephaestin/ cerruloplasmin/ ferroxidase

24
Q

what converts Fe 3+ to Fe 2+

A

Dcytb (duodenal cytochrome like B) aka ferric reductase

25
what allows Fe2+ to go from enterocyte to blood
ferroportin
26
how is transferin uptaken from blood?
occurs by receptor- | mediated endocytosis via transferin receptor (TfR)
27
what transports iron out of edosome?
DMT1
28
what causes Causes hypochromic microcytic anemia
Insufficient dietary iron Menstruating women Aspirin overuse Ulcers of GI tract (Blood loss)
29
what is treatment for hypochromic microcytic anemia
dietary iron supplementation
30
Hereditary Hemochromatosis
Organ dysfunction due to iron overload: cirrhosis, arthritis, endocrinopathy, skin pigmentation, cardiomyopathy
31
what is total body iron inHereditary Hemochromatosis compared to normal
› 3 to 5g normal | › Hereditary Hemochromatosis = 15g
32
Hepcidin
binds to ferroportin and causes internalization | -regulates amount of Fe taken up by body
33
how is hepcidin expression regulated
by Hfe binding to TfR2
34
what happens if Hfe is mutated and can’t bind to TfR2
- cant turn on hepcidin expression - lots of ferroportin - iron overloading
35
what vitamins are required for RBC production
``` vitamin B12 (cobalamin) and folate (folic acid) ```
36
what does deficiency in B12 and folate cause?
megaloblastic anemia | -due to diminished synthesis of DNA
37
Megaloblastic Macrocytic Anemia
Caused by vitamin B12 (cobalamin) and folate (folic acid) deficiency Characterized by large erythrocytes › MCV >100 fL (as high as 140 fL); normal = 80-100 **NORMAL HEMOGLOBIN CONTENT
38
what disease to hyper-segmented neutrophils occur?
Megaloblastic Macrocytic | Anemia:
39
what is the structure of folate?
3 parts: – Pteridine: nitrogen containing ring – p-amino-benzoic acid ring (PABA) – Glutamate residue chains
40
what is the active form of folate?
THF (FH4) (tetrahydrofolate)
41
what is the role of THF (FH4)(tetrhydrofolate)
transfer of carbon units from donor to acceptors (vital role in DNA synthesis)
42
what is the form of dietary folic acid?
FH2 (dihydrofolate)
43
where is folate absorbed
small intestine (jejunum)
44
what organ stores folate?
liver | -stores 5-10 mg folate lasts 3-6 months
45
what is primary circulating form of folate?
N5- | methyl-THF
46
what happens if B12 not available for folate?
folate stuck as N5-methyl-THF : called the folate trap
47
what does vit b12 do to folate?
removes methyl group from N5-methyl-THF to | make methyl-cobalamin (B12-CH3) and release THF (FH4)
48
what does dietary B12 bind to?
R-binder proteins made by gastric mucosa cells
49
what carries b12 to ileum
intrinsic factor made by parietal cells of stomach
50
Pernicious Anemia
Vitamin B12 deficiency can occur due to lack of intrinsic factor (necessary for B12 absorption) - ms a megaloblastic macrocytic anemia
51
how is pernicious anemia diagnosed
schilling test

MCM test 2 (16 decks)

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