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Immunohematology > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

What are the 3 main components to RBC survival?

A

RBC membrane
Hemoglobin structure and function
Cellular metabolism

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2
Q

Red Cell Membrane

A

semipermeable lipid bilayer supported by a protein mesh-like cytoskeleton structure
Phospholipids, the main lipid components
Proteins that extend from the outer surface and span the entire membrane

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3
Q

Glycophorin

A

the principal RBC glycoprotein (20% of the total membrane protein)
Four glycophorin (4) types : A, B, C, D

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4
Q

What does glycophorin do?

A

carry the RBC antigens
serve as receptors, or transport proteins
anchor the plasma membrane envelop to the cytoskeleton network

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5
Q

Are lipids distributed equally throughout the 2 layers of the membrane?

A

No they are not

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6
Q

RBC Lipid Bilayer: Outer layer

A

rich in glycolipids and choline phospholipids
sphingomyelin and phosphatidlycholine

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7
Q

RBC Lipid bilayer: Inner layer

A

rich in phosphatidlyserine, phosphatidylethanolamine (known as amino phospholipids), and phosphotidylinositol

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8
Q

Biochemical composition of RBC membrane

A

52 percent protein
40 percent lipid
8 percent carbohydrate

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9
Q

Normal lifespan of RBC

A

120 days

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10
Q

What is a critical role in cell membrane

A

deformability and permeability

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11
Q

What is freely permeable in a cell membrane?

A

Water
Anions (HCO3- and Cl-)
occurs through a large number of exchange channels

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12
Q

What isn’t freely permeable in an RBC membrane?

A

Cations (Na and K)

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13
Q

erythrocyte intracellular-to-extracellular ratios for sodium and potassium

A

1:12 (Na), respectively
25:1 (K), respectively

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14
Q

How many pumps control the passive influx of Na and K?

A

300 cationic pumps

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15
Q

What is needed for the cationic pumps for Na and K?

A

Needs energy like ATP
Also needs ATPase, a membrane enzyme

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16
Q

What element is also actively transported from the interior of the RBC?

A

Calcium (C++)
through the energy-dependent calcium-ATPase cationic pump

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17
Q

Calmodulin

A

cytoplasmic calcium-binding protein
speculated to control calcium-ATPase pumps
preventing excessive intracellular calcium buildup

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18
Q

What happens with build of calcium?

A

shape changes and loss of deformability

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19
Q

permeability properties of the RBC membrane

A

crucial to preventing colloid osmotic hemolysis
controlling the volume of the red cell

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20
Q

What is the proper Osmotic pressure for RBCs?

A

300 mOs- considered Isotonic

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21
Q

What are the other Osmotic pressures?

A

100 mOs- Hypotonic (Bloated)
500 mOs- Hypertonic (Shriveled)

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22
Q

The energy required for active transport and maintenance of membrane electrochemical gradients is provided by what?

A

ATP

23
Q

What is the metabolic Pathway of ATP for RBCs?

A

Anaerobic, because the function of the red cell is to deliver oxygen, not to consume it

24
Q

How must energy be made in RBC? Why?

A

generated almost exclusively through the breakdown of glucose
Because mature erythrocytes have no nucleus and no mitochondria apparatus

25
Q

What is done in RBC metabolism to maintain hemoglobin function?

A

divided among the anaerobic glycolytic pathway and three ancillary pathways
For the sake of RBC structure and O2 transport

26
Q

What is the main metabolic pathway of RBCs?

A

Glycolysis- Ninety percent of the ATP needed by RBCs is generated

27
Q

What is the remaining ATP made from?

A

The remaining 10% ATP is provided by the pentose phosphate pathway

28
Q

methemoglobin reductase

A

another important pathway
are important in maintaining hemoglobin in a reduced functional state
necessary to maintain the heme iron of hemoglobin in the ferrous (Fe++) functional state

29
Q

Methemoglobin

A

form of the oxygen-carrying hemoglobin, in which the iron in the heme group is in the Fe3+ (ferric) state, not the Fe2+ (ferrous)
Can’t carry O2

30
Q

NADH

A

enzyme responsible for converting methemoglobin back to hemoglobin

31
Q

What happens when NADH is low?

A

Methemoglobin accumulates
loss of oxygen transport capabilities

32
Q

Luebering-Rapaport shunt

A

permits the accumulation of another important red cell organic phosphate, 2,3-diphosphoglycerate (2,3-DPG)

33
Q

2,3-diphosphoglycerate (2,3-DPG)

A

Found in one-to-one molar relationship with hemoglobin, representing approximately 5 mM
profound effect on the affinity of hemoglobin for oxygen

34
Q

What is essential for Hemoglobin Synthesis?

A

Adequate iron delivery and supply
Adequate synthesis of protoporphyrins (the precursor of heme)
Adequate globin synthesis

35
Q

What is the most common Hemoglobin?

A

HbA, 92 to 95 percent of the hemoglobin

36
Q

HbA composition

A

two alpha and two beta chains

37
Q

HbA1c

A

3 to 5 percent of the hemoglobin
Made of 2 alpha chains and 2 glucose chains

38
Q

HbA2

A

2 alpha and delta chains
2-3% of the hemoglobin

39
Q

HbF

A

Fetal Hemoglobin
1 to 2 percent of the hemoglobin
two alpha and two gamma

40
Q

What is hemoglobin’s main function?

A

gas transport: oxygen delivery to the tissues and carbon dioxide (CO2) excretion

41
Q

What is essential about 2,3-DPG?

A

most important controls of hemoglobin affinity for oxygen

42
Q

Tense v Relaxed forms of hemoglobin

A

Tense has a low affinity
Relaxed has a high affinity

43
Q

How is the dissociation and binding of oxygen by hemoglobin represented

A

a sigmoid-curve relationship

44
Q

The normal position of the oxygen dissociation curve depends on three different ligands normally found within the red cell

A

H+ ions
CO2
organic phosphates (2,3-DPG)

45
Q

Of the three ligands for O2 dissociation curve, which is most important?

A

2,3-DPG

46
Q

shift to the right of curve

A

In situations such as hypoxia
an decrease in hemoglobin-oxygen affinity and an increase in oxygen delivery to the tissues
mediated by increased levels of 2,3-DPG

47
Q

Aside from Hypoxia how can a right shift help?

A

a patient who is suffering from an anemia
making the RBCs, although few in number, more efficient
patients may be able to tolerate anemia

48
Q

shift to the left of curve

A

an increase in hemoglobin-oxygen affinity and a decrease in oxygen delivery to the tissues

49
Q

Reasons for left shift

A

Alkalosis
increased quantities of abnormal hemoglobin’s, such as methemoglobin and carboxyhemoglobin
increased quantities of hemoglobin F; or multiple transfusions of 2,3-DPG

50
Q

RED CELL PRESERVATION

A

provide viable and functional blood components for patients needing blood transfusion

51
Q

How is RBC preservation done?

A

focused on maintaining red cell viability during storage and lengthening red cell posttransfusion survival

52
Q

RBC Deformability

A

Loss of ATP
increase in deposition of membrane calcium
causing an increase in membrane rigidity and loss of pliability

53
Q

RBC Deformability: signs

A

“spherocytes” (cells with a reduced surface-to-volume ratio)
“bite cells” removal of a portion of membrane

Immunohematology (16 decks)

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