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Fundamentals Of Pathology > Red Blood Cell Structure And Function > Flashcards

Red Blood Cell Structure And Function Flashcards

1
Q

What three major cell organelles are not present in erythrocytes?

A

Nucleus, mitochondria or ER

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2
Q

How big is a RBC?

A

8 microns

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3
Q

What is the primary function of a RBC?

A

Transport of respiratory gases to and from tissues

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4
Q

What determines the strength and flexibility of a RBC?

A

Cytoskeletal proteins interacting with the membrane lipid bilayer

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5
Q

What does a RBC membrane consist of (%wise)

A

50% proteins
40% lipids
10% carbohydrates

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6
Q

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

A

Glycolipids, glycoproteins and proteins

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7
Q

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

A

Proteins, cholesterol and phospholipids

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8
Q

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

A

Mesh-like cytoskeletal proteins to support lipid bilayer

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9
Q

What proteins do the membrane include?

A

Sphingomyelin
Phosphatidyl ethanolamine
Phosphatidyl serine
Phosphatidyl choline

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10
Q

Where is phosphatidyl normally expressed?

A

Inside layer of membrane

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11
Q

Where is phosphatidyl serine expressed when its undergoing apoptosis?

A

It is expressed to the outer layer

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12
Q

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

A

Macrophages recognise and engulf it to move it from the tissue

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13
Q

What is the breakdown of lipids in the RBC membrane?

A

60% phospholipids
30% cholesterol
10% sphingolipids

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14
Q

Where is there unesterified free cholesterol in RBCs?

A

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

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15
Q

What are the two major integral membrane proteins in RBCs?

A

Glycophorins

Band 3 anion transporters

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16
Q

What are the three types of glycophorins?

A

A, B and C

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17
Q

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

A

Na/K ATPase, aquaporin surface receptors

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18
Q

What are peripheral proteins?

A

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

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19
Q

What does the cytoskeleton do in the RBC?

A

Acts as a tough framework to support the bilayer

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20
Q

What are the 4 major peripheral proteins in RBCs?

A

Spectrin
Ankyrin
Protein 4.1
Actin

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21
Q

What is spectrin composed of?

A

Alpha and beta chains

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22
Q

What is the most abundant peripheral protein?

A

Spectrin

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23
Q

What does spectrin do in the RBC membrane?

A

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

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24
Q

What does spectrin control?

A

Biconcave shape and deformability of a cell

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25
Q

What does ankyrin primarily do in the RBC?

A

Anchors lipid bilayer to membrane skeleton

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26
Q

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

A

By interacting with spectrin and band 3

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27
Q

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

A

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

28
Q

What does actin do in the RBC membrane?

A

Contraction and relaxation of the membrane

29
Q

What maintains the surface area in the RBC membrane

A

Strong cohesion between bilayer and membrane skeleton

30
Q

Where are carbohydrates found in the RBC?

A

External surface

31
Q

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

A

Glycosylation

32
Q

How many monosaccharide units may carbohydrates contain?

A

2-60

33
Q

Name the monosaccharides found on the erythrocyte membrane (8)

A 
Galactose
Mannose
Fructose 
N-acetyl galactosamine
Glucuronic acid
Glucose
Sialic acid
N-acetyl glucosamine
34
Q

Where are blood group antigens found?

A

On the RBC membranes and determines the blood group

35
Q

Name the examples of RBC membrane protein antigens (3)

A

Rhesus, Duffy and Kidd

36
Q

Name the examples of RBC membrane carbohydrate antigens (2)

A

ABO, Lewis

37
Q

What are the 4 functions of RBC membranes?

A

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

38
Q

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

A

Membrane surface receptors

39
Q

Why does RBC membrane provide deformability and elasticity?

A

Allows for passage through micro vessels (capillaries)

40
Q

What does the RBC membrane shape provide?

A

The optimum surface area to volume ratio for respiratory exchange

41
Q

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

A

An accumulation of cholesterol in the RBC membrane

42
Q

What is an acanthocyte?

A

RBC with increased cholesterol

43
Q

What do acanthocytes look like?

A

Distorted- kinda spiky

44
Q

What causes target cells?

A

Increase in cholesterol and phospholipids

45
Q

What is a microcyte?

A

Where most RBCs are smaller than normal

46
Q

What causes microcytes?

A

Less haemoglobin

47
Q

What is hypochromia?

A

Less haemoglobin

48
Q

What is a macrocyte?

A

Most RBCs are bigger than usual

49
Q

What causes macrocytes?

A

More haemoglobin

50
Q

What is anisocytosis?

A

Different red cell sizes

51
Q

What is poiliocytosis?

A

Different red cell shapes

52
Q

What is hereditary spherocytosis?

A

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

53
Q

Where are the mutations in hereditary elliptocytosis?

A

A or B spectrin mutation

54
Q

What does hereditary spherocytosis look like?

A

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

55
Q

What does hereditary elliptocytosis look like?

A

Long thin cells

56
Q

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

A

Deformation whilst maintaining constant surface area

57
Q

What is cytoplasmic viscosity determined by in RBC membrane?

A

MCHC

58
Q

How does MCHC determine cytoplasmic viscosity in RBC membrane?

A

As MCHC revises, viscosity rises exponentially

59
Q

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

A

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

60
Q

What are the 4 key metabolic pathways in erythrocytes?

A

Glycolytic
Hexose monophosphate shunt
Methemoglobin reductase pathway
Lumbering rapaport shunt

61
Q

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

A

90-95%

62
Q

Where does the glycolytic pathway function in RBCs?

A

The maintenance of RBC shape, flexibility and the cation pumps

63
Q

What provides the reducing power for NADPH in the RBC?

A

Pentose phosphate pathway

64
Q

What does the RBC use GSH for?

A

To protect it from oxidative damage

65
Q

What does the methemoglobin pathway do?

A

Maintains iron in the ferrous (Fe2+) state

66
Q

What happens in the absence of methemoglobin reductase?

A

Methemoglobin accumulates and cannot carry oxygen

67
Q

What does the lumbering rapoport shunt do?

A

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

Fundamentals Of Pathology (20 decks)

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