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Liz's Hematology Module 1 > RBC Metabolism > Flashcards

RBC Metabolism Flashcards

1
Q

3 areas crucial for RBC metabolism crucial for normal survival and function

A
  1. RBC membrane
  2. Hemoglobin structure and function
  3. RBC metabolic pathways
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2
Q

2 major proteins of the RBC membrane

A
  1. Glycophorin

2. Spectrin

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3
Q

Proteins that extend from outer surface through lipid bilayer of cell membrane

A

Integral protein

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4
Q

Proteins that line the inner membrane surface to form the membrane cytoskeleton

A

Peripheral protein

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5
Q

Glycophorin

- Integral or peripheral protein?

A

Integral

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6
Q

Spectrin

- Integral or peripheral protein?

A

Peripheral

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7
Q

Major functionof glycophorin

A

Accounts for most of membrane sialic acid and gives RBC its negative charge (zeta potential); location of many RBC Ags

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8
Q

Major function of spectrin

A

Strengthens RBC membrane (shape and stability) and preserves deformability (pliability)

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9
Q

Acanthocyte

- Structural membrane defect

A

Lack of beta lipid protein

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10
Q 
Bite cell (schistocyte)
- Structural membrane defect
A

↓ spectrin (not as pliable, sluggishly travel through splenic cords); RE cells try to phagocytize them

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11
Q

Spherocytes

- Structural membrane defect

A

↓ spectrin (not as pliable, sluggishly travel through splenic cords); RE cells try to phagocytize them

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12
Q

Target cells

A

Accumulation of cholesterol in membrane

↑ surface area → ↓ intracellular hemoglobin → target cells)

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13
Q

Protein carrier that delivers iron to RBC membrane for hemoglobin synthesis

A

Transferrin

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14
Q

2 major tissues in the body where heme synthesis occurs

A
  1. Erythroid marrow (nRBCs)

2. Liver

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15
Q

Diagram sequence leading to heme synthesis beginning w/ succinyl coenzyme A + glycine and ending w/ heme

A
  1. Glycine & succinyl CoA
  2. ALA
  3. Porphobilinogen (PBG)
  4. Uroporphyrinogen
  5. Coproporphrinogen
  6. Protophorphyrinogen + Fe = protoporphyrin…to form heme
    INSERT PIC HERE
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16
Q

3 processes necessary for normal hemoglobin production

A
  1. Adequate iron delivery and supply
  2. Adequate synthesis or portoporphyrins (precursor to heme)
  3. Adequate globin synthesis
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17
Q

Overview of hemoglobin biosynthesis (nRBCs)

A
  1. Begins in mitochondria of cell
  2. Intermediate steps in cytosol
  3. Process completed in mitochondria w/ insertion of iron into protophorphyrin ring to produce heme
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18
Q

aka heme

A

Porphyrin

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19
Q

Describe the chemical structure of heme

A
  • Molecule made up of 4 pyrrole rings

- Arrangement of 4 nitrogen atoms in center enables porphyrins to chelate metal atoms (like iron)

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20
Q

Why does a patient w/ lead poisoning present “ringed sideroblasts”?

A
  • Lead blocks incorporation of iron into heme molecule

- Mitochondrial buildup of iron causes “ringed sideroblasts” → M/H anemia

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21
Q

Why is freshly voided urine from a porphyria patient not red in color?

A

It isn’t oxidized (will initially be yellow); 1 hour later will be burgundy

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22
Q

Porphyrinogen

  • Precursor to ____
  • Colorless, non-fluorescence, highly ____
  • Quickly and ____ oxidizes to ____
A

Porphyrin; unstable; irreversibly; porphyrin

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23
Q

Porphyrin

  • Stable?
  • Fluorescent?
  • Color?
A

Yes, it’s stable
Yes, it’s fluroescent
Color is pinkish-red (“port wine”) in color

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24
Q

Disorder of heme synthesis

A

Porphyria

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25
Q

How can someone develop porphyria?

A
  • May be inherited or acquired

- Acquired via lead poisoning or liver disease

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26
Q

Where does the abnormal accumulation of prophyrins or porphyrin precursors occur?

A
  • Erythroid marrow

- Liver

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27
Q

3 hemoglobins found exclusively in the embryo

A
  1. Gower 1
  2. Gower 2
  3. Portland
28
Q

Hemoglobin A

- Globin chain composition and percentage of adult hemoglobin

A

2 alpha chains
2 beta chains
> 95%

29
Q

Hemoglobin B

- Globin chain composition and percentage of adult hemoglobin

A

2 alpha chains
2 delta chains
1.5-3.0%

30
Q

Hemoglobin F

- Globin chain composition and percentage of adult hemoglobin

A

2 alpha chains

2 gamma chains

31
Q

Oxygen affinity in the relaxed form of hemoglobin

A

↑ oxygen affinity

- Binds to iron; as soon as one atom of iron binds to O2, three more bind causing a confirmation change

32
Q

The relaxed form of hemoglobin is found in ____

A

Arterial blood

33
Q

Another name for the relaxed form of hemoglobin

A

Oxyhemoglobin

34
Q

Oxygen affinity in the tense form of hemoglobin

A

↓ oxygen affinity

- Results in the unloading of O2 by hemoglobin; binding of 2,3-DPG occurs

35
Q

The tense form of hemoglobin is found in ____

A

Veins and tissues

36
Q

Another name for the tense form of hemoglobin

A

Deoxyhemoglobin

37
Q

What does pO2 represent on an oxygen dissociation curve?

A

The partial pressure or tension of oxygen in the tissues plotted against % of O2 saturation

38
Q

On an oxygen dissociation curve, what does p50 represent?

A

pO2 = 26.6 mmHg when hemoglobin is 50% saturated w/ O2

39
Q

On an oxygen dissociation curve, what is a “shift-to-the-right?”

A

The releasing of O2 in the tissues

40
Q

“Shift-to-the-right”

  • Hb’s affinity for O2
  • pH
  • 2,3-DPG
  • Temperature
A

↓ Hb’s affinity for O2
↓ in pH
↑ in 2,3-DPG
↑ in temperature

41
Q

On an oxygen dissociation curve, what is a “shift-to-the-left?”

A

O2 uptake in the lungs

42
Q

“Shift-to-the-left”

  • Hb’s affinity for O2
  • pH
  • 2,3-DPG
  • Temperature
A

↑ Hb’s affinity for O2
↑ in pH
↓ in 2,3-DPG
↓ in temperature

43
Q

3 abnormal hemoglobins taht are unable to transport or deliver oxygen

A
  1. Carboxyhemoglobin
  2. Methemoglobin
  3. Sulfhemoglobin
44
Q

Main source of ATP production in the mature RBCs

A

Anaerobic glycolysis in the mitochondria

45
Q

Metabolic pathway that generates most of the RBC’s ATP

A

Embden-Meyerhof

46
Q

4 major RBC metabolic pathways

A
  1. Embden-Meyerhof
  2. Hexose Monophosphate Shunt
  3. Methemoglobin Reductase Pathway
  4. Leubering -Rapaport Shunt
47
Q

Major function of Embden-Meyerholf pathway

A

Produces 90% of the energy needed by the RBC’s via anaerobic glycolysis

48
Q

Major function of hexose monophosphate shunt

A

Protects RBCs from environmental oxidants

49
Q

Major function of methemoglobin reductase pathway

A

Maintains iron in the ferrous (2+) state in order for it to carry O2

50
Q

Major function of Leubering-Rapaport shunt

A

Synthesis of 2,3-DPG

51
Q

Changes in RBCs leading to its demise at 120 days

A

Senescence and then phagocytized by RES cells

52
Q

Breakdown of senescent RBCs outside of the blood vessel w/in the cells of the RES

A

Extravascular hemolysis

53
Q

Breakdown of senescent RBCs w/in the blood vessel

A

Intravascular hemolysis

54
Q

___% of the destruction of senescent RBCs occurs by extravascular hemolysis

A

90%

55
Q

Steps involved in extravascular hemolysis

A
  1. RES cells phagocytize RBCs
  2. Iron is coupled to transferrin and returned to BM and globin is returned to amino acid pool
  3. Protophorphyrin ring of heme is disassembled and biliverdin is converted to bilirubin
  4. Bilirubin is coupled to albumin and transported to liver
  5. In the liver, bilirubin is conjugated to bilirubin glucuronide, converted to urobiliogen, and excreted
56
Q

____% of the destruction of senescent RBCs occurs by intravascular hemolysis

A

10%

57
Q

Steps involved in intravascular hemolysis

A
  1. RBCs break in the lumen of vessel
  2. Haptoglobin picks up free Hb
  3. Hp-Hb complex goes to liver for futher catabolism…following same process as in extravascular hemolysis (do you remember it?)
58
Q

Haptoglobin is ____ in the presence of intravascular hemolysis

A

Decreased

59
Q

Why is haptoglobin decreased in the presence of intravascular hemolysis?

A

B/c it’s busy binding up the free hemoglobin

60
Q

What happens when haptoglobin is decreased in the presence of intravascular hemolysis?

A

Unbound hemoglobin dimers appear in the plasma

61
Q

“Free heme”/unbound hemolgobin dimers in the plasma is called ____

A

Hemoglobinemia

62
Q

“Free heme” is ____ by the ____ and excreted as either ____ or hemosiderin in the urine

A

Filtered; kidneys; hemoglobin

63
Q

Presence of hemoglobin in the urine

A

Hemoglobinuria

64
Q

T/F, under normal conditions hemoglobinemia and hemoglobinuria should be seen

A

False

65
Q

Protein carrier for bilirubin

A

Albumin

66
Q

Protein carrier for hemoglobin

A

Haptoglobin

67
Q

Protein carrier for iron

A

Transferrin

Liz's Hematology Module 1 (15 decks)

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