Red cell membrane and its congenital disorders

Question 1

What percent of RBC weight is accounted for by red cell memebrane

Answer 1

1%

Question 2

Functions of red cell memebrane

Answer 2

Maintains RBC integrity
provides flexibility so RBC can adjudt its shape\
Durability
Tensile strength
Maintains its structure
Metabolism
Acid base hemeostasis through pumps present in it

Question 3

Cell membrane bilipid layer made mainly of

Answer 3

Cholesterol
Phospholipids
integral proteins for tensile strength and flexibility
Membrane skeleton for structure

Question 4

lipids make up this percentage of red cell membrane

Answer 4

50-60%

Mainly phosphatidyl choline; inositol; serine; ethanolamine
Sphingomyelin

Question 5

Function of cholesterol in membrane

Answer 5

Ensures membrane fluidity

Question 6

Phospholipids distribution in Red cell membrane

Answer 6

Asymetrically distributed

phosphatidyl serine; ethanolamine inwards

Phosphatidyl choline , sphingomyelin outwards

Question 7

Membrane proteins of red cell

Answer 7

1. integral membrane proteins
   eg .Band 3,Glycophorins ,Kidd ,Duffy, Rh proteins, Lutheran glycoprotein

2.Peripheral membrane proteins
eg sceptrin, ankyrin, protein 4.1, protein 4.2

Question 8

Integral memebrane proteins

Answer 8

, a permanent part of membrane

Question 9

most abundant integral glycoprotein

Answer 9

Glycophorin

Question 10

Glycophorin receptors

Answer 10

provide acces for various infectious agents including plasmodium falciparum

Question 11

Glycophorins

Answer 11

carry a number of blood group antigens

Question 12

Major anion exchanger in cell membrane

Answer 12

Band 3

Question 13

Peripheral protiens are

Answer 13

Transiently binding proteins that attach either to integral proteins or membrane itself

Question 14

Spectrin has how many subunits

Answer 14

2. alpha and beta

Question 15

Spectrin binds the following proteins

Answer 15

Protein 4.1
Ankyrin
Actin

Question 16

Function of spectrin

Answer 16

Maintains cellular shape

Structural support

Question 17

Function of ankyrin

Answer 17

Provides primary linkage between membrane skeleton via spectrin binding
Provided primary linkage between lipid bilayer via band 3

Question 18

Abnormalities of ankyrin produces

Answer 18

Hereditary spherocytosis

Question 19

Protein 4.1 function

Answer 19

Links spectrin actin membrane skeleton to lipid bilayer

Question 20

Protein 4.2 function

Answer 20

Stabilizes spectrin -actin - ankyrin association with band 3

Question 21

in membrane organization; vertical interactions

Answer 21

stabilize lipid bilayer

Question 22

in membrane organization horizontal interactions

Answer 22

maintain structure of cell membrane and gives it a high tensile strength

Question 23

Defects in red cell membrane leading to hemolytic anemia

Answer 23

hereditary spherocytosis
hereditary elliptocytosis
hereditary pyropoikilocytosis

Question 24

What is hereditary spherocytosis

Answer 24

A membrane defect that makes RBC spherical with increased osmotic fragility

Question 25

What sex is affected most by hereditary spherocytosis

Answer 25

Both sexes affected equally

Question 26

What membrane protein deficiency causes hereditary spherocytosis

Answer 26

Ankyrin, spectrin, protein 4.2

Also proteins involved in vertical interactions

Question 27

Pathophysiology of hereditary spherocytosis

Answer 27

Defects in proteins involved in vertical interactions between membrane skeleton and lipid bilayer—>release of parts of lipid bilayer not supported by membrane skeleton—>Become spherical and less flexible—>difficult to pass through splenic microcirculation—>slowly passes through splenic microcirculation–>Ample time is gotten in this environment of low pH and glucose to break it down

Question 28

potassium and water levels in hereditary spherocytosis

Answer 28

diminished

Question 29

Clinical features of hereditary spherocytosis

Answer 29

Late detection
Symptoms of anemia is slight, Hb doesnt fall below 7.5g/dl
Jaundice
Splenomegaly
Gall stones
Leg ulcers
Aplastic anemia precipitated by parvovirus

Question 30

Lab findings for hereditary spherocytosis

Answer 30

Aneamia
Numerous spherocytes with no area of central pallor and decreased diameter
high MCHC
high osmotic fragility
Mean cell fragility greater than 0.45
high reticulocyte count

Question 31

Management of hereditary spherocytosis

Answer 31

folic acid

Splenectomy if severe

Question 32

Hereditary spherocytosis common in

Answer 32

people of North European descent

Question 33

Hereditary elliptocytosis common in

Answer 33

People of african and mediterranean descentdescent

Question 34

Hereditary elliptocytosis confers resistance to this disease

Answer 34

Malaria

Question 35

People with Hereditary elliptocytosis usually present as

Answer 35

Asymptomatic or with severe life threatening situation

Question 36

Method of inheritance of hereditary elliptocytosis

Answer 36

Autosomal dominant

Question 37

is hereditary spherocytosis milder than hereditary elliptocytosis

Answer 37

no. less cases of splenectomy recorded in elliptocytosis

Question 38

Defects in what interactions cause hereditary elliptocytosis

Answer 38

horizontal interactions

Question 39

Management of hereditary elliptocytosis

Answer 39

Because its usually mild, its asymptomatic and detected accidentally.

Those with severe symptoms can however undergo splenectomy or blood transfusions

Question 40

Hereditary pyropoikilocytosis is seen in these patients

Answer 40

burn patients