RBC membrane Structure Flashcards

1
Q

Average volume of RBC

A

90 fL (range: 80-100 fL)

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2
Q

Average surface area of RBC

A

140 μm2

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3
Q

________________of RBCs facilitates its oxygen-carbon dioxide transport function.

A

Biconcave disc shape of RBCs

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4
Q

allows RBCs to adjust to small vessels in the microvasculature and still maintain a constant surface area: volume ratio

A

Deformability

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5
Q

RBC deformability depends on:

A
  1. RBC geometry
  2. Relative cytoplasmic (hemoglobin) viscosity
  3. Membrane elasticity (pliancy)
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6
Q

Normal erythrocyte Hgb concentration has a _______ viscosity (fluid)

A

low

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7
Q

↓ water and hemoglobin (precipitated, polymerized, or crystallized) →

A

Less deformable which leads to cell lysis

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8
Q

Precipitated hemoglobin leads to the formation of

A

Heinz bodies

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9
Q

Polymerized hemoglobin leads to the formation of

A

Hemoglobin S

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10
Q

Crystallized hemoglobin leads to the formation of

A

Hemoglobin C

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11
Q

Changes in the surface area to volume ratio causes?

A

RBC fragmentation and lysis

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12
Q

Fragmentation is due to?

A

The decrease in surface area

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13
Q

Lysis is due to?

A

The increase in cell volume

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14
Q

3 basic functions of the RBC membrane

A
  1. Regulates osmotic pressure
  2. Regulates cation concentration
  3. Regulates gas concentrations
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15
Q

Percentage of lipids

A

40%

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16
Q

Predominant in lipids

A

phospholipids and cholesterol

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17
Q

Arranged in a double layer called lipid bilayer leaflet |provides membrane fluidity

A

Phospholipids

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18
Q

Predominant in external surface of Phospholipids

A

phosphatidylcholine and sphingomyelin (with 5% glycolipid)

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19
Q

sugar-bearing lipids
support carbohydrate side chains
anchors glycocalyx
bears blood group antigens

A

Glycolipid

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20
Q

Predominant in the internal surface of phospholipids

A

phosphatidylethanolamine and phosphatidylserine

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21
Q

regulates membrane fluidity and membrane permeability
maintains surface area:volume ratio

A

Cholesterol

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22
Q

Charac of cholesterol

A

Esterified
Hydrophobic
Equally distributed between the outer and inner layer
evenly distributed within each layer

23
Q

Cholesterol content depends on

A

plasma cholesterol, bile acids, activity of LCAT (lecithin-cholesterol acyltransferase)

24
Q

Abnormal L/S ratio

A

Acanthocyte

25
Q

↑ cholesterol, phospholipids

A

Codocyte

26
Q

↓ cholesterol

A

Ovalocyte

27
Q

Cholesterol confers tensile strength to the lipid bilayer

A

↑ cholesterol → ↑ membrane strength → ↓ elasticity

28
Q

Percentage of carbohydrates

A

8%

29
Q

🖝 layer of carbohydrates whose net negative charge prevents microbial attack and protects the RBC from mechanical damage
🖝 surface carbohydrates joined with glycolipids

A

Glycocalyx

30
Q

Percentage of proteins

A

52%

31
Q

contains sialic acid which gives RBCs a negative charge

A

Integral Proteins/Transmembrane Proteins

32
Q

Functions of Integral Proteins/Transmembrane Proteins

A

Transport site
Adhesion site
Signaling receptors

33
Q

principal integral CHON

A

Band 3

34
Q

2 macromolecular complexes of integral proteins:

A

Ankyrin complex
Protein 4.1 complex/Actin junctional complex

35
Q

Major components of ankyrin complex

A

Band 3 multimers
Protein 4.2

36
Q

Major components of Protein 4.1 complex/Actin junctional complex

A

Band 3 dimers
Protein 4.2
Adducin

37
Q

Other transmembrane CHONs

A

Aquaporin 1
Glut-1
glycophorins
Na+, K+-ATPase
Ca+2-
ATPase
blood group antigen
ICAM-4

38
Q

🞍 Prevents loss of lipid bilayer
🞍 Provides membrane structural integrity

A

Integral CHONs + peripheral CHONs

39
Q

principal cytoskeletal CHONs

A

a-spectrin and β-spectrin

40
Q

Other cytoskeletal CHONs

A

F-actin (band 5)
adducin
ankyri
dematin
tropomodulin
tropomyosin

41
Q

Functions of Peripheral Proteins/Cytoskeletal Proteins

A

Spectrin stabilization
Membrane deformation

42
Q

RBC membrane is impermeable to

A

• Na+
• K+
• Ca2+

43
Q

RBC membrane is permeable to

A

• H2O
• HCO3-
• Cl-

44
Q

Transmembrane protein; water transporter

A

Aquaporin 1

45
Q

What happens when there is a decrease of Aquaporin 1

A

Hereditary spherocytosis

46
Q

Intracellular (Na: K ratio)

A

1:12

47
Q

Extracellular (Na: K ratio)

A

25:1

48
Q

controls active transport of sodium & potassium

A

Na+, K+ - ATPase

49
Q

↑ Na → water enters the cell →

A

Cell lysis

50
Q

↑ K →

A

Cell shrinkage

51
Q

maintains low intracellular Ca2+ levels (5-10 µmol/L)

A

Ca2+ - ATPase

52
Q

controls the function of Ca2+ - ATPase

A

Calmodulin

53
Q

↑ Ca → ↓ membrane stability cell →

A

cell becomes less deformable

54
Q

Colloid Osmotic Hemolysis:

A

ATP loss or Pump damage → Na+, Ca2+ influx → water enters the cell → swelling (spheroid) → rupture