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HEMATOLOGY > 4. ERYTHROCYTE MEMBRANE STRUCTURE > Flashcards

4. ERYTHROCYTE MEMBRANE STRUCTURE Flashcards

1
Q

Average volume RBC

A

90 fL (range: 80-100 fL)

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2
Q

Characteristic of RBC which facilitates its oxygen-carbon dioxide transport function

A

Biconcave disc shape

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3
Q

Average surface area of RBC

A

140 μm2

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4
Q

RBC plasma membrane thickness

A

5 µm thick

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5
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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6
Q

RBC deformability depends on:

A

RBC geometry

Relative cytoplasmic (hemoglobin) viscosity

Membrane elasticity (pliancy)

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7
Q

Changes in the surface area to
volume ratio causes

A

RBC fragmentation
and lysis

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8
Q

due to ↓ surface area

A

Fragmentation

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9
Q

due to ↑ cell volume

A

Lysis

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10
Q

Relative cytoplasmic (hemoglobin) viscosity → MCHC

A

32% – 36%

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11
Q

Normal erythrocyte Hgb concentration has a

A

low viscosity (fluid)

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12
Q

Precipitated hemoglobin →

A

Heinz bodies

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13
Q

Polymerized hemoglobin

A

Hb S

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14
Q

Crystallized hemoglobin

A

Hb C

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15
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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16
Q

RBC MEMBRANE COMPOSITION AND STRUCTURE

A

Lipids (40%)
Carbohydrate (8%)
Protein (52%)

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17
Q

Predominant lipids in RBCs

A

phospholipids and cholesterol

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18
Q

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

A

Phospholipids

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19
Q

External surface of lipid bilayer leaflet predominant composition

A

phosphatidylcholine and sphingomyelin (with 5% glycolipid)

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20
Q

sugar-bearing lipids | support carbohydrate side chains | anchors

A

Glycolipid

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21
Q

bears blood group antigens

A

glycocalyx

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22
Q

Internal surface of lipid bilayer leaflet predominant composition

A

phosphatidylethanolamine and phosphatidylserine

23
Q

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

A

Cholesterol

24
Q

Cholesterol content depends on

A

plasma cholesterol, bile acids, activity of LCAT (lecithincholesterol acyltransferase)

25
Q

↑ cholesterol, phospholipids

26
Q

Abnormal L/S ratio

A

Acanthocyte

27
Q

↓ cholesterol

28
Q

↑ cholesterol → ↑ membrane strength results to

A

↓ elasticity

29
Q

layer of carbohydrates whose net negative charge prevents microbial attack and protects
the RBC from mechanical damage

A

Glycocalyx

30
Q

surface carbohydrates joined with glycolipids

A

Glycocalyx

31
Q

contains sialic acid which gives RBCs a negative charge

A

Integral Proteins/Transmembrane Proteins

32
Q

Integral Proteins/Transmembrane Proteins Functions

A

🞍 Transport site
🞍 Adhesion site
🞍 Signaling receptors

33
Q

principal integral CHON

34
Q

2 macromolecular complexes of integral proteins:

A

Ankyrin complex
Protein 4.1 complex/Actin junctional complex

35
Q

Ankyrin complex Major components →

A

band 3 multimers and protein 4.2

36
Q

Protein 4.1 complex/Actin junctional complex: Major components →

A

band 3 dimers,
protein 4.2 and adducin

37
Q

Other transmembrane CHONs:

A

:Aquaporin 1,
Glut-1,
glycophorins,
Na+,
K+-ATPase,
Ca+2-
ATPase,
blood group antigens (e.g., Kell, Kidd, Duffy, Rh, RhAG),
ICAM-4

38
Q

🞍 Prevents loss of lipid bilayer
🞍 Provides membrane structural integrity

A

Integral CHONs + peripheral CHONs:

39
Q

principal cytoskeletal CHONs

A

(alpha)-spectrin and β-spectrin (bands 1 and 2, respectively)

40
Q

Other cytoskeletal CHONs:

A

F-actin (band 5),
adducin,
ankyrin,
dematin,
tropomodulin,
tropomyosin

41
Q

Peripheral Proteins/Cytoskeletal Proteins Functions

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

↓ aquaporin 1

A

hereditary spherocytosis

46
Q

ATP-Dependent Cation Pumps

A

Na+, K+ - ATPase
Ca2+ - ATPase

47
Q

Intracellular (Na: K ratio)

48
Q

Extracellular (Na: K ratio)

49
Q

controls active transport of sodium & potassium
* ↑ Na → water enters the cell → cell lysis
* ↑ K → cell shrinkage

A

Na+, K
+ - ATPase

50
Q

maintains low intracellular Ca2+ levels

A

Ca2+ - ATPase

51
Q

intracellular Ca2+ levels

A

5-10 µmol/L

52
Q

controls the function of Ca2+ - ATPase

A

Calmodulin

53
Q

↑ Ca → ↓ membrane stability cell results to

A

cell becomes less deformable

54
Q

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

A

Colloid Osmotic Hemolysis:

HEMATOLOGY (10 decks)

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