Red Blood Cell Structure And Function

Question 1

What three major cell organelles are not present in erythrocytes?

Answer 1

Nucleus, mitochondria or ER

Question 2

How big is a RBC?

Answer 2

8 microns

Question 3

What is the primary function of a RBC?

Answer 3

Transport of respiratory gases to and from tissues

Question 4

What determines the strength and flexibility of a RBC?

Answer 4

Cytoskeletal proteins interacting with the membrane lipid bilayer

Question 5

What does a RBC membrane consist of (%wise)

Answer 5

50% proteins
40% lipids
10% carbohydrates

Question 6

What is the outer hydrophilic portion of a RBC membrane composed of?

Answer 6

Glycolipids, glycoproteins and proteins

Question 7

What is the central hydrophobic portion of a RBC membrane composed of?

Answer 7

Proteins, cholesterol and phospholipids

Question 8

What is the inner hydrophilic portion of a RBC membrane composed of?

Answer 8

Mesh-like cytoskeletal proteins to support lipid bilayer

Question 9

What proteins do the membrane include?

Answer 9

Sphingomyelin
Phosphatidyl ethanolamine
Phosphatidyl serine
Phosphatidyl choline

Question 10

Where is phosphatidyl normally expressed?

Answer 10

Inside layer of membrane

Question 11

Where is phosphatidyl serine expressed when its undergoing apoptosis?

Answer 11

It is expressed to the outer layer

Question 12

What happens when phosphatidyl serine is expressed on the outer layer?

Answer 12

Macrophages recognise and engulf it to move it from the tissue

Question 13

What is the breakdown of lipids in the RBC membrane?

Answer 13

60% phospholipids
30% cholesterol
10% sphingolipids

Question 14

Where is there unesterified free cholesterol in RBCs?

Answer 14

Between the uncharged phospholipids of outer layer (phosphatidylcholine and sphingomyelin)
Between the charged phospholipids of inner layer

Question 15

What are the two major integral membrane proteins in RBCs?

Answer 15

Glycophorins

Band 3 anion transporters

Question 16

What are the three types of glycophorins?

Answer 16

A, B and C

Question 17

Give some other integral proteins (that aren’t glycophorins or band 3)

Answer 17

Na/K ATPase, aquaporin surface receptors

Question 18

What are peripheral proteins?

Answer 18

Limited to the cytoplasmic surface of membrane and forms the RBC cytoskeleton

Question 19

What does the cytoskeleton do in the RBC?

Answer 19

Acts as a tough framework to support the bilayer

Question 20

What are the 4 major peripheral proteins in RBCs?

Answer 20

Spectrin
Ankyrin
Protein 4.1
Actin

Question 21

What is spectrin composed of?

Answer 21

Alpha and beta chains

Question 22

What is the most abundant peripheral protein?

Answer 22

Spectrin

Question 23

What does spectrin do in the RBC membrane?

Answer 23

Binds with other peripheral proteins to form the cytoskeletal network of microfilaments

Question 24

What does spectrin control?

Answer 24

Biconcave shape and deformability of a cell

Question 25

What does ankyrin primarily do in the RBC?

Answer 25

Anchors lipid bilayer to membrane skeleton

Question 26

How does ankyrin anchor the lipid bilayer to the membrane skeleton?

Answer 26

By interacting with spectrin and band 3

Question 27

What does protein 4.1 do in the RBC membrane (2)?

Answer 27

Link the cytoskeleton to the membrane by means of it’s associations with glycophorin Stabilises interaction of spectrin with actin

Question 28

What does actin do in the RBC membrane?

Answer 28

Contraction and relaxation of the membrane

Question 29

What maintains the surface area in the RBC membrane

Answer 29

Strong cohesion between bilayer and membrane skeleton

Question 30

Where are carbohydrates found in the RBC?

Answer 30

External surface

Question 31

How are carbohydrate groups attached to proteins and lipids in RBC?

Answer 31

Glycosylation

Question 32

How many monosaccharide units may carbohydrates contain?

Answer 32

2-60

Question 33

Name the monosaccharides found on the erythrocyte membrane (8)

Answer 33

``` Galactose Mannose Fructose N-acetyl galactosamine Glucuronic acid Glucose Sialic acid N-acetyl glucosamine ```

Question 34

Where are blood group antigens found?

Answer 34

On the RBC membranes and determines the blood group

Question 35

Name the examples of RBC membrane protein antigens (3)

Answer 35

Rhesus, Duffy and Kidd

Question 36

Name the examples of RBC membrane carbohydrate antigens (2)

Answer 36

ABO, Lewis

Question 37

What are the 4 functions of RBC membranes?

Answer 37

Provides shape Provides deformability and elasticity Regulates intracellular cation concentration Acts as the interface between the cell and its environment

Question 38

How does the RBC membrane act as an interface between the cell and its environment

Answer 38

Membrane surface receptors

Question 39

Why does RBC membrane provide deformability and elasticity?

Answer 39

Allows for passage through micro vessels (capillaries)

Question 40

What does the RBC membrane shape provide?

Answer 40

The optimum surface area to volume ratio for respiratory exchange

Question 41

What does an increase in free plasma cholesterol in the RBC membrane result in?

Answer 41

An accumulation of cholesterol in the RBC membrane

Question 42

What is an acanthocyte?

Answer 42

RBC with increased cholesterol

Question 43

What do acanthocytes look like?

Answer 43

Distorted- kinda spiky

Question 44

What causes target cells?

Answer 44

Increase in cholesterol and phospholipids

Question 45

What is a microcyte?

Answer 45

Where most RBCs are smaller than normal

Question 46

What causes microcytes?

Answer 46

Less haemoglobin

Question 47

What is hypochromia?

Answer 47

Less haemoglobin

Question 48

What is a macrocyte?

Answer 48

Most RBCs are bigger than usual

Question 49

What causes macrocytes?

Answer 49

More haemoglobin

Question 50

What is anisocytosis?

Answer 50

Different red cell sizes

Question 51

What is poiliocytosis?

Answer 51

Different red cell shapes

Question 52

What is hereditary spherocytosis?

Answer 52

Defects in ankyrin, A or B spectrin, band 3 and protein 4.2

Question 53

Where are the mutations in hereditary elliptocytosis?

Answer 53

A or B spectrin mutation

Question 54

What does hereditary spherocytosis look like?

Answer 54

RBCs look like doughnuts (Hb gathers round the outside and none in the middle)

Question 55

What does hereditary elliptocytosis look like?

Answer 55

Long thin cells

Question 56

What does the SA:vol ratio facilitate in RBC membrane?

Answer 56

Deformation whilst maintaining constant surface area

Question 57

What is cytoplasmic viscosity determined by in RBC membrane?

Answer 57

MCHC

Question 58

How does MCHC determine cytoplasmic viscosity in RBC membrane?

Answer 58

As MCHC revises, viscosity rises exponentially

Question 59

What does metabolism provide the energy for in RBC (4)?

Answer 59

Maintenance of canon pumps Maintenance of RBC integrity and deformability Maintenance of Hb in a reduced state Maintenance of reduced sulfhydryl groups in Hb and other proteins

Question 60

What are the 4 key metabolic pathways in erythrocytes?

Answer 60

Glycolytic Hexose monophosphate shunt Methemoglobin reductase pathway Lumbering rapaport shunt

Question 61

How much energy (%) does the glycolytic pathway generate for RBC?

Answer 61

90-95%

Question 62

Where does the glycolytic pathway function in RBCs?

Answer 62

The maintenance of RBC shape, flexibility and the cation pumps

Question 63

What provides the reducing power for NADPH in the RBC?

Answer 63

Pentose phosphate pathway

Question 64

What does the RBC use GSH for?

Answer 64

To protect it from oxidative damage

Question 65

What does the methemoglobin pathway do?

Answer 65

Maintains iron in the ferrous (Fe2+) state

Question 66

What happens in the absence of methemoglobin reductase?

Answer 66

Methemoglobin accumulates and cannot carry oxygen

Question 67

What does the lumbering rapoport shunt do?

Answer 67

Permits the accumulation of 2,3-DPG which is essential for maintaining normal oxygen tension, regulating haemoglobin affinity