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CPR > Erythrocyte Biochemistry (Part 1) > Flashcards

Erythrocyte Biochemistry (Part 1) Flashcards

1
Q

During erythropoiesis, an erythroblast transitions into a?

A

Normoblast

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2
Q

During erythropoiesis, what happens to a normoblast?

A

Its nucleus is expelled and it turns into a Reticulocytes and then eventually a RBC (erythrocyte)

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3
Q

During erythropoiesis, when is the majority of the Hemoglobin (Hb) synthesized?

A

BEFORE the nucleus is expelled from the normoblast

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4
Q

Fetal Hb

A

2 alpha chains and 2 gamma chains

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5
Q

Adult Hb (majority form)

A

2 alpha chains and 2 beta chains

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6
Q

Adult Hb (minority form)

A

2 alpha chains and 2 delta chains

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7
Q

Hemoglobin has 4 subunits (2alpha and 2beta), what is contained within each subunit?

A

1 heme bound to 1 iron (ferrous - Fe2+)

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8
Q

Before oxygen is bound, describe the orientation of the iron in Hb

A

OUTSIDE the plane of porphyrin

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9
Q

After oxygen is bound, describe the orientation of the iron in Hb

A

INSIDE the plane of porphyrin

- Pulls proximal Histidine down

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10
Q

Once oxygen is bound to the iron atom in Hb, what does this do to the proximal Histidine?

A

Pulls it down

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11
Q

What shape is the myoglobin oxygen dissociation curve?

A

Hyperbolic

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12
Q

What shape is the hemoglobin oxygen dissociation curve?

A

Sigmoidal

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13
Q

Why is the hemoglobin oxygen dissociation curve sigmoidal?

A

Positive Cooperativity!

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14
Q

What is Positive Cooperativity with Hb?

A

The binding of 1 oxygen to 1 heme facilitates binding of another oxygen to another heme

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15
Q

Why is Positive Cooperativity important?

A

Enhances oxygen delivery to tissues!

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16
Q

This molecule DECREASES oxygen affinity for Hb so more oxygen is delivered to tissues

A

2,3-BPG

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17
Q

Bohr effect results in a ____ shift of the oxygen dissociation curve

A

RIGHT

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18
Q

Describe the Bohr effect

A

Carbon dioxide and H+ produced by working tissues stimulates Hb to release oxygen
– Decreases Hb affinity for oxygen

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19
Q

Does HbF bind well to 2,3-BPG?

A

NO – thus the affinity for oxygen remains high in HbF

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20
Q

At what amino acid position # is the mutation for sickle cell anemia?

A

6

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21
Q

What is the mutation in sickle cell anemia?

A

Glutamic acid (-) is switched with Valine (hydrophobic)

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22
Q

Sickle shaped erythrocytes ______ circulation

A

Impede

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23
Q

Research on sickle cell anemia is being done to try and induce expression of?

A

HbF

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24
Q

Fe 2+

A

Ferrous

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25
Q

Fe 3+

A

Ferric

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26
Q

Most of iron is contained in Hb, where is the rest?

A

Stored in cells of intestines, liver, spleen and bone marrow

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27
Q

Heme iron

A

Fe 2+

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28
Q

Where is Heme iron found?

A

Animal products

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29
Q

Non-Heme iron

A

Fe 3+

30
Q

Where is Non-Heme iron found?

A

Plant products

31
Q

What form of iron can be taken up from the intestinal lumen into Enterocytes?

A

Fe 2+ - Heme iron

32
Q

What enzyme converts Non-Heme iron (Fe 3+) to Fe 2+?

A

Ferric Reductase

33
Q

What transporter takes up Fe 2+ into Enterocytes once its converted from Fe 3+ in the intestinal lumen?

A

DMT-1

34
Q

What enzyme in the Enterocyte converts Fe 2+ to Fe 3+?

A

Ferroxidase

Cerruloplasmin

35
Q

If Fe 3+ is going to be stored in the Enterocyte, what is it stored as?

A

Ferritin

36
Q

What is Ferritin (storage form of Fe 3+) degraded to?

A

Hemosiderin

37
Q

What transporter takes Fe 2+ from the Enterocyte to the blood?

A

Ferroportin

38
Q

What does Ferroportin require?

A

Hephastin

39
Q

Once Fe 2+ is in the blood stream, it is converted to ____ by _____

A

Fe 3+

Ferroxidase (Cerruloplasmin)

40
Q

What is Fe 3+ bound to in the blood?

A

Transferrin

41
Q

Transferrin’s job?

A

Bind and transfer Fe 3+ to target tissues

42
Q

How is Transferrin-Fe3+ taken up by target cells?

A

Receptor Mediated Endocytosis via TfR receptor

43
Q

What causes Transferrin and its receptor to dissociate once in the endosome during receptor mediated endocytosis?

A

LOW pH

44
Q

The endosome containing Transferrin-Fe3+ docks where in the cell?

A

Mitochondria

45
Q

How does Hepcidin regulate Iron homeostasis?

A

It will bind Ferroportin and degrade it so iron cannot get into the blood stream

46
Q

When iron is HIGH, what are the levels of Hepcidin, Ferroportin and iron absorption?

A

Hepcidin = HIGH
Ferroportin = LOW
Iron absorption = LOW

47
Q

When iron is LOW, what are the levels of Hepcidin, Ferroportin and iron absorption?

A

Hepcidin = LOW
Ferroportin = HIGH
Iron Absorption = HIGH

48
Q

What regulates iron homeostasis and where?

A

Hepcidin

– At Ferroportin

49
Q

What controls Hepcidin levels?

A

HFE

50
Q

Hypochromic microcytic anemia

A

Iron Deficiency

51
Q

Hemochromatosis

A

Iron Overload

52
Q

How is Hemochromatosis inherited?

A

Autosomal Recessive

53
Q

Deficiency in Folate AND Vitamin B12 (cobalamin) causes?

A

Megaloblastic Macrocytic Anemia

54
Q

How do Erythrocytes appear with Megaloblastic Macrocytic Anemia?

A

LARGE - with normal Hb content

55
Q

Describe Folate Metabolism

A

Folate
Dihydrofolate (DHF)
Tetrahydrofolate (THF)

56
Q

What is the active form of Folate?

A

THF

57
Q

What is the enzyme that converts Folate to DHF and THF?

A

Dihydrofolate Reductase

58
Q

What is the main role of THF?

A

DNA synthesis

59
Q

What is the main circulating form of Folate in the blood?

A

N^5 - methyl - THF

60
Q

What does N^5 - methyl - THF require to be converted to THF, its active form?

A

Vitamin B12 (cobalamin)

61
Q

What is the folate trap?

A

Without Vitamin B12, Folate will be stuck inactively in the form of N^5 - methyl - THF

62
Q

What inhibits DNA synthesis by inhibiting Dihydrofolate reductase?

A

Methotrexate

63
Q

Where is Vitamin B12 (cobalamin) found?

A

ONLY Animal products

64
Q

Describe Vitamin B12 metabolism

A

B12 binds to R-binder proteins
B12 binds to Intrinsic fact and dissociates from R-binder
B12-IF travels to Ileum and enters blood stream
Transcobalamin II carries complex in blood
Complex taken up by cells via Receptor mediated Endocytosis

65
Q

What carries the Vitamin B12 - Intrinsic Factor Complex in the blood?

A

Transcobalamin II

66
Q

Pernicious Anemia

A

Vitamin B12 Deficiency due to lack of Intrinsic Factor

67
Q

Is Pernicious Anemia a type of Megaloblastic Macrocytic Anemia?

A

Yes

68
Q

What is the test to test for Pernicious Anemia?

A

Schiling Test

69
Q

1st step of Schilling test

A

Administer radioactive B12

  • Measure urine
    • If B12 is present = Normal Absorption (def. diet)
    • If B12 NOT present = NOT Absorbed - move on to step 2
70
Q

2nd step of Schilling Test

A

Administer radioactive B12 + INTRINSIC FACTOR

  • Measure urine
  • If B12 is present = Pernicious anemia due to lack of intrinsic factor!

CPR (48 decks)

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