4. ERYTHROCYTE MEMBRANE STRUCTURE

Question 1

Average volume RBC

Answer 1

90 fL (range: 80-100 fL)

Question 2

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

Answer 2

Biconcave disc shape

Question 3

Average surface area of RBC

Answer 3

140 μm2

Question 4

RBC plasma membrane thickness

Answer 4

5 µm thick

Question 5

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

Answer 5

Deformability

Question 6

RBC deformability depends on:

Answer 6

RBC geometry

Relative cytoplasmic (hemoglobin) viscosity

Membrane elasticity (pliancy)

Question 7

Changes in the surface area to
volume ratio causes

Answer 7

RBC fragmentation
and lysis

Question 8

due to ↓ surface area

Answer 8

Fragmentation

Question 9

due to ↑ cell volume

Answer 9

Lysis

Question 10

Relative cytoplasmic (hemoglobin) viscosity → MCHC

Answer 10

32% – 36%

Question 11

Normal erythrocyte Hgb concentration has a

Answer 11

low viscosity (fluid)

Question 12

Precipitated hemoglobin →

Answer 12

Heinz bodies

Question 13

Polymerized hemoglobin

Answer 13

Hb S

Question 14

Crystallized hemoglobin

Answer 14

Hb C

Question 15

3 Basic Functions of the RBC Membrane

Answer 15

1. Regulates osmotic pressure
2. Regulates cation concentration
3. Regulates gas concentrations

Question 16

RBC MEMBRANE COMPOSITION AND STRUCTURE

Answer 16

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

Question 17

Predominant lipids in RBCs

Answer 17

phospholipids and cholesterol

Question 18

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

Answer 18

Phospholipids

Question 19

External surface of lipid bilayer leaflet predominant composition

Answer 19

phosphatidylcholine and sphingomyelin (with 5% glycolipid)

Question 20

sugar-bearing lipids | support carbohydrate side chains | anchors

Answer 20

Glycolipid

Question 21

bears blood group antigens

Answer 21

glycocalyx

Question 22

Internal surface of lipid bilayer leaflet predominant composition

Answer 22

phosphatidylethanolamine and phosphatidylserine

Question 23

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

Answer 23

Cholesterol

Question 24

Cholesterol content depends on

Answer 24

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

Question 25

↑ cholesterol, phospholipids

Answer 25

Codocyte

Question 26

Abnormal L/S ratio

Answer 26

Acanthocyte

Question 27

↓ cholesterol

Answer 27

Ovalocyte

Question 28

↑ cholesterol → ↑ membrane strength results to

Answer 28

↓ elasticity

Question 29

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

Answer 29

Glycocalyx

Question 30

surface carbohydrates joined with glycolipids

Answer 30

Glycocalyx

Question 31

contains sialic acid which gives RBCs a negative charge

Answer 31

Integral Proteins/Transmembrane Proteins

Question 32

Integral Proteins/Transmembrane Proteins Functions

Answer 32

🞍 Transport site 🞍 Adhesion site 🞍 Signaling receptors

Question 33

principal integral CHON

Answer 33

Band 3

Question 34

2 macromolecular complexes of integral proteins:

Answer 34

Ankyrin complex Protein 4.1 complex/Actin junctional complex

Question 35

Ankyrin complex Major components →

Answer 35

band 3 multimers and protein 4.2

Question 36

Protein 4.1 complex/Actin junctional complex: Major components →

Answer 36

band 3 dimers, protein 4.2 and adducin

Question 37

Other transmembrane CHONs:

Answer 37

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

Question 38

🞍 Prevents loss of lipid bilayer 🞍 Provides membrane structural integrity

Answer 38

Integral CHONs + peripheral CHONs:

Question 39

principal cytoskeletal CHONs

Answer 39

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

Question 40

Other cytoskeletal CHONs:

Answer 40

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

Question 41

Peripheral Proteins/Cytoskeletal Proteins Functions

Answer 41

🞍 Spectrin stabilization 🞍 Membrane deformation

Question 42

RBC membrane is impermeable to:

Answer 42

* Na+ * K+ * Ca2+

Question 43

RBC membrane is permeable to:

Answer 43

* H2O * HCO3- * Cl

Question 44

❖ Transmembrane protein; water transporter

Answer 44

Aquaporin 1

Question 45

↓ aquaporin 1

Answer 45

hereditary spherocytosis

Question 46

ATP-Dependent Cation Pumps

Answer 46

Na+, K+ - ATPase Ca2+ - ATPase

Question 47

Intracellular (Na: K ratio)

Answer 47

1:12

Question 48

Extracellular (Na: K ratio)

Answer 48

25:1

Question 49

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

Answer 49

Na+, K + - ATPase

Question 50

maintains low intracellular Ca2+ levels

Answer 50

Ca2+ - ATPase

Question 51

intracellular Ca2+ levels

Answer 51

5-10 µmol/L

Question 52

controls the function of Ca2+ - ATPase

Answer 52

Calmodulin

Question 53

↑ Ca → ↓ membrane stability cell results to

Answer 53

cell becomes less deformable

Question 54

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

Answer 54

Colloid Osmotic Hemolysis: