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02. MCM Test 2 > 10. Erythrocyte Biochemistry > Flashcards

10. Erythrocyte Biochemistry Flashcards

1
Q

What are the seven stages of erythrocyte differentiation?

A
  1. Hemocytoblast
  2. Pro-erythroblast
  3. Early Erythroblast
  4. Late Erythroblast
  5. Normoblast
  6. Reticulocyte
  7. Erythrocyte
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2
Q

At what differentiation stage does an erythrocyte discharge its nucleus?

A

The normoblast stage.

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3
Q

What does the early erythroblast do to prepare the cell to become an erythrocyte?

A

Synthesizes ribosomes

These will later be producing Hb

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4
Q

What two stages of erythrocyte differentiation accumulate hemoglobin?

A

Late erythroblast and normoblast

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5
Q

What is the Hb structure for adult Hb?

A

2x Alpha-globin 2x beta-globin

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6
Q

Is heme hydrophobic or hydrophilic?

A

Hydrophobic

(it hides, nestled inside the globin protiens)

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7
Q

What three types of Hb are only found in embryos?

What globin units are unique to these Hb’s?

A
  1. Hb Gower 1
  2. Hb Gower 2
  3. Hb Portland

zeta and epsilon

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8
Q

What is the globin configuration for HbF (fetal)?

A

2x alpha globin, 2x gamma globin

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9
Q

As far as globin synthesis embryologically;

Which globin is produced first as epsilon and zeta are being destroyed?

Which globin comes up next, and then falls off after birth?

Which globin comes up after birth to replace it?

A

Alpha is produced first, and stays high

Gamma is produced next and falls off at birth

Beta production increases after birth, while gamma production falls off.

(These don’t happen immediately, but are the trends)

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10
Q

What two chromosomes hold the globin genes?

A

Chromosome 16 and 11

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11
Q

What current research is underway to possibly treat sickle cell anemia?

What compound are they trying to use to accomplish this?

A

Trying to induce HbF (using the patient’s wild type gamma-globin to replace their mutant beta-globin)

Hydroxyurea

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12
Q

Which histidine is the F8 histidine in hemoglobin?

What does it do?

A

The proximal histidine.

It is bound to the heme group

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13
Q

Which hemoglobin subunit is the distal histidine attached to?

What does it do?

A

The E7 histidine

Stabalizes oxygen

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14
Q

What sort of curve does oxygen binding to myoglobin display?

A

Hyperbolic curve

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15
Q

What sort of curve does oxygen binding to hemoglobin display?

Why does it display this curve?

A

Sigmoidal (allosteric) binding curve

Because there is cooperativity between O2 diatoms. One binding makes it easier for another to bind.

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16
Q

What is the name for the effect of pH on oxygen binding to hemoglobin?

A

Bohr’s Effect

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17
Q

Besides availability of oxygen, what important factor changes in the peripheral tissues to assist in the release of O2?

A

pH!

Peripheral tissue is more acidid, and the H+ causes the distal histidine to release the oxygen.

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18
Q

What does 2,3-BPG do to the oxygen binding curve?

What is it doing?

A

Shifts it to the right.

Decreasing the affinity of hemoglobin for oxygen.

19
Q

Why might hemoglobin be more effective at releasing oxygen into exercising tissues?

A

Because the pO2 is lower there, so O2 can more freely dissociate.

20
Q

What is different about the binding affinity of fetal hemoglobin to adult hemoglobin?

What accounts for this difference?

A

Fetal hemoglobin must have a higher binding affinity for O2 than the mother’s Hb.

Fetal hemoglobin does not bind well to 2,3-BPG

21
Q

What two protiens store iron?

A

Ferritin and hemosiderin

Hemosiderin is just degraded ferritin

22
Q

Where do you find the majority of iron in the body?

A

As Hemoglobin

23
Q

When we eat plants, what form is the iron in?

What form does it need to be in to enter the enterocyte?

What transport protien allows it to enter?

What changes it from one form to the other?

A

Plant iron is as Fe3+

We only absorb Fe2+

Divalent Transporter 1

Ferric Reductase changes between the two.

24
Q

What form does iron need to be in to be stored in ferritin?

A

Fe3+

25
Q

What enzyme transports iron out of the enterocyte?

What form must the iron be in to be transported by this protien?

A

Ferroportin

Fe2+

26
Q

What form must iron be in to be transported in the blood?

What protien assists with blood transport of iron?

A

Fe3+

Transferrin

27
Q

What enzyme changes Fe2+ into Fe3+ in the blood, to be transported by transferrin?

A

Ferroxidase: Ceruloplasmin / Hephaestin

  • Ferroxidase is a familiy of enzymes. Ceruloplasmin is a member of that family, and so is Hephaestin.*
  • Hephaestin is named for Hephaestus, Greek god of iron working*
  • # Darrenfacts*
28
Q

How does transferin enter a cell?

What special can happen to bring iron directly to mitochondria, where heme is made?

A

Receptor mediated endocytosis (Transferrin receptors create clatherin coated endosomes)

The endosome can dock directly to the mitochondria, releasing transferring right there - ready to go.

29
Q

How much iron is qualified as hereditary hemochromatosis?

A

Greater than 15 grams

30
Q

What is the main function of the hormone Hepcidin?

A

Degradation of ferroportin by tagging it for internalization and proteolysis. (Stops iron from leaving the enterocyte)

31
Q

What does HFE do?

What does its deficiency cause?

A

Continues the signal of Hepcidin by binding to Tfr2.

Mutation in HFE can cause Hemochromatosis.

  • HFE’s real name is “Human Hemochromatosis Protien.” The astute among you may notice that those letters don’t line up. The reason for that is that HFE actually STANDS FOR High Fe, because that’s when it’s active.*
  • # Darrenfacts*
32
Q

What sort of anemia might B12 and Folate deficiency cause?

What is this disease due to?

A

Megaloblastic macrocytic anemia with normal hemoglobin content

Diminished DNA synthesis

33
Q

What other finding (not related to red blood cells) might you find in Megaloblastic macrocytic anemia?

A

Hyper-segmented neutrophils (more than 5 lobes)

34
Q

What is the active form of folate, and what does it do?

A

Tetrahydrofolate (THF)

Serves a vital role in DNA synthesis.

(Transfers single carbons)

35
Q

What enzyme converts folate to dihydrofolate, and dihydrofolate to trihydrofolate?

A

Dihydrofolate reductase (does both reactions using NADPH)

36
Q

Once we get to tetrahydrofolate, what two important paths can it go down?

What do each of those paths do?

A
  1. It can become 5,10 Methylene THF

This accepts a carbon from serine but can get stuck. :(

  • MethylENE takes from serINE or makes dTMP but if not for cobalaMINE (sp) it’ll never be SEEN again.*
    2. It can become 5,10 Methenyl THF

This participates in nucleotide synthesis

37
Q

In what form is folate absorbed in the intestine?

Why is this important to know?

A

N5-methyl-THF

Cobalamin is needed just to transform dietary folate!

38
Q

What specific action does cobalamin perform in regards to folate?

A

It demethylates it!

39
Q

In what foods can you find cobalamin?

What produces cobalamin?

A

Animal foods only (almost 100% sure this isn’t true, but it’s on the slide - so…)

Microorganisms

40
Q

What is necessary for cobalamin absorption?

What cell produces that?

Where in the gut is it absorbed?

A

Intrinsic factor

Parietal cells

The Ilium

41
Q

What is the name for B12 related anemia?

A

Pernicious Anemia

42
Q

What test is used to determine the etiology of B12 deficiency?

A

Schilling test

43
Q

If your schilling test shows radioactive B12 in the urine before you add intrinsic factor, what is the result?

A

The patient is absorbing B12 normally, and they have a B12 deficient diet.

44
Q

If you give someone a load of B12, along with a little bit of labeled B12, and you don’t see it in their urine, what are the two possibilities for that patient?

What should you test next?

What are the possible results for that test?

A

Either they are not absorbing B12 properly, or they are not producing Intrinsic Factor.

Do the same test, but give the patient Intrinsic factor as well.

If the addition of Intrinsic Factor shows B12 in their urine, then it’s an Intrinsic Factor deficiency. Otherwise, they just can’t absorb B12.

02. MCM Test 2 (14 decks)

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