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Haemotology > Red Blood Cells > Flashcards

Red Blood Cells Flashcards

1
Q

How long is the lifespan of a healthy RBC?

A

120 days

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2
Q

Name the vitamins and minerals required for erythropoiesis (RBC production).

A
  • Iron
  • Cobalt
  • Vitamin C
  • Copper
  • Vitamin E
  • Vitamins B6 and B12
  • Thiamine
  • Riboflavin
  • Folic Acid
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3
Q

How many erythrocytes are produced each day?

A

5x10^10 erythrocytes

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4
Q

What is the disorder associated with elevated RBC in the BM as a consequence of increased red cell destruction?

A

Erythrocytosis

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5
Q

What is the name of the disorder associated with hyperproliferation of RBCs?

A

Polycythaemia

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6
Q

What organelles are absent in the mature RBC?

A
  • Nucleus

- Mitochondria

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7
Q

Why do RBCs lack a nucleus?

A

The absence of a nucleus allows RBCs to possess a physical flexibility that enables them to squeeze through the smallest capillaries to deliver oxygen to tissues.

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8
Q

What is the disadvantage of not having a nucleus?

A

Increased susceptibility to pathogens or extremes in physiology.

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9
Q

Name the three parts of the RBC plasma membrane.

A

(1) A phosphodiester lipid bilayer
(2) Proteins and Glycoproteins
(3) An internal cytoskeletal scaffold

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10
Q

Name the 8 membranous proteins associated with the CO2/HCO3- metabolon.

A

(1) Band3 (AE1)
(2) Carbonic Anhydrase II
(3) Glycophorin B
(4) CD47
(5) 4.2
(6) Ankyrin
(7) RhAG
(8) AQP1

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11
Q

What is the role of Band3?

A

Anion transporter associated with the exchange of the bicarbonate ion for the chloride ion.

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12
Q

What is the role of Carbonic anhydrase II?

A

Enzyme which catalyses the conversion of Carbon dioxide and water to bicarbonate and protons.

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13
Q

What is the role of Glycophorin B?

A

Coupled with glycophorins A, C and D, glycophorin B links the membrane to the internal cytoskeleton.

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14
Q

What is the role of protein 4.2?

A

Bind ankyrin.

Possibly also contributes to the link between the anion exchanger and the Rh proteins

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15
Q

What is the role of ankyrin?

A

Ankyrin links the anion exchanger (band 3 and associated proteins) to the Rh proteins.

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16
Q

What is the role of Rh associated glycoprotein?

A

RhAg is essential for the expression of Rh molecules.

Also associated with the Exchange of carbon dioxide

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17
Q

What is the role of the Aquaporin 1?

A

AQP1 is a transporter of water, oxygen and carbon dioxide.

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18
Q

What are the alpha and beta spectrin?

A

Structural components of the matrix that provide skeletal support for the biconcave structure of the RBC.

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19
Q

What is the purose of the biconcave shape?

A

It allows the cell to have a 40% increase in surface area.

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20
Q

Why is a blood transfusion less often rejected when compared to an organ?

A

RBCs lack the HLA (Human leukocyte Antigen) cell surface protein associated with initiating the immune response.

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21
Q

What cell synthesises haemoglobin and where in the cell does this synthesis take place?

A

Erythroblasts - mitochondria and cytoplasm.

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22
Q

What two components comprise the haemoglobin molecule?

A

(1) Haem

(2) globin tetramer

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23
Q

Which structural component of haemoglobin binds iron?

A

The haem.

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24
Q

What vitamins are essential for the synthesis of haem?

A

Vitamin B6 and 12 and folate

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25
Q

What is the role of Vitamin B6?

A

Vitamin B6 is a cofactor for the enzyme Methylmalonyl-CoA Mutase associated with Haem production.

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26
Q

What is the role of Vitamin B12?

A

Vitamin B 12 is the cofactor ofthe enzyme “aminolaevulinic acid synthase” which converts succinyl CoA and glycine into Aminolaevulinic acid during the production of haem.

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27
Q

What is the role of the enzyme porphobilinogen synthase in the production of haem?

A

Porphobilinogen synthase catalyses the dehydration and condensation reaction of two aminolaevulinic acid molecules in the cytoplasm of a RBC to form porphobilinogen.

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28
Q

How much iron is absorbed in the diet per day in a healthy adult?

A

15 mg/day

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29
Q

What enzyme controls the conversion of ferric iron into ferrous ion within the lumen of the intestine?

A

Ferroreductase enzymes

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30
Q

What enzyme present on the luminal surface of enterocytes is associated with the internalisation of ferrous iron?

A

Divalent metal transporter 1

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31
Q

What enzyme is responsible for the liberation of iron from haem within the enterocyte?

A

Haemoxygenase-1

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32
Q

What enzyme is associated with the transport of iron out of the enterocyte into the plasma of the blood?

A

Ferroportin

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33
Q

What enzyme is important in the regulation of ferroportin?

A

Hepcidin

34
Q

What enzyme is associated with the conversion of ferrous iron into ferric ion within the plasma?

A

Caeruloplasmin and ferrooxidase enzymes

35
Q

What proteins in the plasma transport iron?

A

Transferrin
Albumin
Lactoferrin

36
Q

What receptor does transferrin bind to to internalise iron into the RBC?

A

transferrin receptor

37
Q

What proteins does iron bind to to be stord?

A

Ferritin and Haemosiderin

38
Q

What organs store iron?

A

Mainly the liver but also the spleen, pancreas and bone marrow.

39
Q

In what cell and where in the cell is globin synthesised ?

A

Erythroblasts and nucleated RBCs in the cytoplasm

40
Q

What globin chains are associated with haemoglobin A, A2 and F?

A

HbA: Two alpha globin molecules and two beta globin molecules

HBA2: Two alpha globin chains and two delta globin chains/

HBF: Two alpha globin chains and two gamma globin chains.

41
Q

What globin chains are associated with fetal haemoglobin?

A

Mainly 2 alpha globin and 2 gamma globin

but beta, epsilon and zeta globin also observed.

42
Q

What is carboxyhaemoglobin and how much of this compound is present in normal individuals?

A

Carbon monoxide bound to haemoglobin

2% of total haemoglobin

43
Q

Why can a carboxyhaemoglobin value of more than 80% lead to death?

A

Carbon monoxide binds haemoglobin with an affinity 200x that of oxygen. This binding is irreversible ad as such reduced numbers of haemoglobin are free to deliver oxygen to tissues.

44
Q

What common trait is associated with elevated levels (5%) of carboxyhaemoglobin?

A

smoking

45
Q

What is Carbaminohaemoglobin?

A

Haemoglobin bound to Carbon Dioxide.

46
Q

What is methaemoglobin?

A

Haemoglobin reversibly bound to ferric iron and not ferrous iron like it is normally bound to.

47
Q

Why does methaemoglobin only comprise 2% or less of haemoglobin numbers?

A

Oxygen does not bind to ferric iron and therefore methaemoglobin is functionally useless.

48
Q

What is sulphaemoglobin?

A

Haemoglobin irreversibly bound to sulfur

49
Q

How do mature RBCs get their energy?

A

Embden-Meyerhof glycolytic pathway

50
Q

What two points is ATP formed during glycolysis?

A

1,3-Diphosphoglycerate -> 3-Phosphoglycerate

Phosphophenolpyruvate -> Pyruvate

51
Q

What is the phenomenom of facilitation in terms of haemoglobin-oxygen binding?

A

Each haemoglobin can bind to four oxygen molecules,
Facilitation refers to the phenomenom by which the affinity of haemoglobin-oxygen binding increases with an increased amount of bound oxygen molecules.

52
Q

Why does facilitation occur?

A

Oxygenation causes a conformational change known as allosterism so that the beta chains come closer together, and the solvent-filled channel between the subunits close up.

53
Q

What is considered a high pO2?

A

90 mmHg

54
Q

What is considered a low pO2?

A

15 mmHg

55
Q

How is an individual’s oxygen carrying abilities measured?

A

In terms of their p50 - the partial pressure of oxygen at which 50% of haemoglobin is oxygenated.

56
Q

What is the average healthy p50 in adults and fetus?

A

27 mmHg in adults

18 mmHg in fetus

57
Q

What are the implications of a right shifted oxygen dissociation curve?

A
  • More oxygen is required to oxygenate 50% of haemoglobin (higher p50)
  • These haemoglobin molecules give up oxygen more readily to peripheral tissue.
58
Q

What are the implications of a left-shifted oxygen dissociation curve?

A
  • Less oxygen is required to oxygenate 50% of haemoglobin (lower p50)
  • These haemoglobin molecules are less willing to give up oxygen to peripheral tissue.
59
Q

Increasing and decreasing p50 shifts the oxygen dissociation curve to which side?

A

Increasing: Right

Decreasing: Left

60
Q

What factors can influence the oxygen dissociation curve?

A

pH:

  • Acidosis inside RBC: Shifts curve to the right
  • Alkalosis inside RBC: Shifts the curve to the left

Temperature:

  • High: Shifts the curve to the right
  • Low: Shifts the curve to the left

Carbon Dioxide:

  • High: Shifts the curve to the right
  • Low Shifts the curve to the left

Carbon Monoxide:

  • High: Shifts the curve to the left
  • Low: Shifts the curve to the right

2,3-Diphosphoglycerate:

  • High: Shifts the curve to the right
  • Low: Shifts the curve to the left.
61
Q

Why does 2,3-DPG promote oxygen release from haemoglobin?

A

2,3-DPG binds deoxyhaemoglobin with higher affinity than oxyhaemoglobin and therefore promotes oxygen dissociation from haemoglobin.

62
Q

What happens to lactate in the RBC once it has been produced by glycolysis?

A

It exits the RBC via monocarboxylate transporter

63
Q

What does the RBC use ATP for?

A
  1. Sodium/Potassium Pump
  2. Phosphorylation of membrane lipids (PIP2 required to maintain biconcave shape)
  3. Actin in the cytoskeleton requires ATP
64
Q

What causes sickle cell anaemia?

A

Glu6Val Mutation

Glutamine is mutated to Valine at position 6 of the Beta globin chain.

65
Q

What causes the RBC to adopt the sickle cell shape in sickle cell anaemia?

A

Sickle cell haemoglobin (HbS) becomes insoluble under certain conditions including hypoxia, acidosis and increased temperature.
Insoluble HbS polymerises to form the sickle cell shape.

66
Q

What are the clinical consequences of sickle celled RBCs?

A
  • Occlusion of the blood vessels
  • Infarction / Tissue hypoxia
  • Build up of Reticulocytes which also contribute to vascular occlusion
  • Stroke
  • Haemolytic anaemia
67
Q

What tests are done to confirm sickle cell anaemia?

A
  • Wet preparations

- HPLC

68
Q

Describe the three tests associated with wet preparations?

A

(1) Mixing blood sample with a reducing agent such as Sodium metabisulfate to reduce osygen concentration and observe whether cells adopt the sickle shape.
(2) Mixing the blood sample with saponin to lyse cells, sodium dithionate to deoxygenate them and a phosphate buffer. Within the phosphate buffer, after an incubation period normal RBC will lyse and the solution will become clear however sickle RBCs will not lyse and the solution will remain cloudy.
(3) Within the buffer solution described above, the presence of sickle cells will give a dark red purple precipitate.

69
Q

What are the benefits and disadvantages of wet precipitation?

A

Quick and cheap

Prone to erroe

70
Q

What is the haematological presentation of sickle cell anaemia?

A
  • Haemolytic anaemia
  • Haemoglobin concentration between 60-90g/L
  • Elevatied reticulocyte count of 10-20%
  • Haemocrit between 0.18-0.30L/L
71
Q

What is hereditory spherocytosis?

A

RBC deform into a sphere - disease inherited due to an autosomal dominant mutation in genes associated with the interaction of the plasma membrane and the skeletal membrane.

Proteins include:

  • Alpha and beta spectrins
  • Ankyrin
  • Band 3
  • Protein 4.2
72
Q

What is the lifespan of a RBC of spherocytosis?

A

6-20 days

73
Q

What is the clinical presentation of spherocytosis?

A

Haemolytic anaemia and jaundice

74
Q

How are sufferers of spherocytosis treated?

A
  • Splenectomy

- Folic Acid supplements

75
Q

What is the haematological presentation of spherocytosis?

A
  • Increased reticulocyte count (5-20%)
  • Low haemoglobin (70g/L)
  • Reduced MCV
  • Raised MCHC (360g/L)
  • Blood film shows densde micropherocytes with no central pallor
76
Q

What is hereditory elliptocytosis?

A

RBC of abnormal morphology such that they appear elongated due to an inability to return to their normal shape after extravasion.

77
Q

What causes elliptocytosis?

A

Mutation in the gene coding for band 4.1 such that spectrin heterodimers cannot assemble properly causing a defect in the skeletal membrane.

78
Q

What are the haematological presentation of elliptocytosis?

A
  • Possible haemoltic anaemia (if homozygous)

- 80% of cells are oval/eliptical

79
Q

What is hereditory stomatocytosis?

A

Impaired transport of sodium and potassium cations

80
Q

What causes hereditory stomatocytosis?

A

Autosomal dominant mutation in the genes associated with membrane components, most often Band 3 or Rh protein resulting in a change in specificity of ion transporters such that they lose their specificity.

81
Q

What is pyropoikilocytosis and how is it caused?

A

Red cell fragmentation caused by a defect in alpha-spectrinn due to a autosomal recessive mutation.

Haemotology (1 decks)

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