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Haematology > Haemoglobin > Flashcards

Haemoglobin Flashcards

1
Q

where does haemoglobin synthesis occur?

A

in the cytoplasm

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2
Q

how is Haem synthesised?

A

iron brought into mitochondria and is used the the Krebs cycle
leaves mitochondria to join with porphyrin ring

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3
Q

how much O2 will bind to 1g Hb?

A

1.34ml

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4
Q

what is the structure of haemglobin?

A

tetramer made up of 2 alpha globin and 2 (B, D, Y) globin chains
one haem group attached to each globin chain
each haem group contains a Fe ion

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5
Q

what are the major forms of Haemoglobin?

A

HbA
HbA2
HbF

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6
Q

what is the structure of HbA?

A

2 alpha chains and 2 beta chains; α2β2

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7
Q

what is the structure of HbA2?

A

2 alpha and 2 delta; α2δ2

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8
Q

what is the structure of HbF?

A

2 alpha and 2 gamma; α2γ2

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9
Q

HbF is also known as

A

foetal haemoglobin

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10
Q

which haemoglobin is the main form in adults?

A

HbA

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11
Q

alpha globin synthesis is controlled by which gene?

A

chromosome 16 (2 alpha genes per chromosome (4 per cell))

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12
Q

beta globin synthesis is controlled by which gene?

A

chromosome 11 (One beta gene per chromosome (2 per cell))

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13
Q

what is haemoglobin cooperativity?

A

binding affinity for oxygen is increased by the oxygen saturation of the molecule, with the first molecules of oxygen bound allowing for positive conformational changes for the binding sites for the next ones

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14
Q

what shape is the oxygen binding curve of haemoglobin?

A

S shaped

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15
Q

what is the role of iron?

A 
Oxygen transport - Reversible oxygen binding by haemoglobin
Electron transport (e.g. mitochondrial production of ATP) - Ferric (Fe3+  )  and ferrous forms ( Fe2+   )
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16
Q

iron is present in which body compounds?

A
  • Haemoglobin
  • Myoglobin
  • Enzymes eg cytochromes
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17
Q

where is iron absorbed?

A

duodenum

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18
Q

iron absorption is enhanced by…

A

Haem vs non-haem iron
dedicated haem iron transporter
Ascorbic acid
Alcohol

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19
Q

iron absorption is inhibited by…

A

Tannins eg tea
Phytates eg cereals, bran, nuts and seeds
Calcium eg dairy produce

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20
Q

how is iron absorbed?

A

o Duodenal cytochrome B
o DMT (divalent metal transporter) -1
o Ferroportin

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21
Q

how is iron absorption regulated?

A

o Hepcidin

22
Q

what is the mechanism of hepicidin?

A

Produced in liver in response to iron load and inflammation
Binds to ferroportin and causes its degradation
Iron ‘trapped’ in duodenal cells and macrophages

23
Q

how is functional iron status assessed?

A

Haemoglobin concentration

24
Q

how is transport iron status assessed?

A

% saturation of transferrin with iron

25
Q

how is storage iron status assessed?

A

serum ferritin, tissue biopsy

26
Q

what is the role of transferrin?

A

Transports iron from donor tissues (macrophages, intestinal cells and hepatocytes) to tissues expressing transferrin receptors (especially erythroid marrow)

27
Q

what is the structure of transferrin?

A

Protein with two binding sites for iron atoms

28
Q

how does transferrin saturation measure iron supply?

A

serum iron/total iron binding capacity(to transferrin) x 100 %

29
Q

what are the different types of transferrin?

A

holotransferrin (iron bound), apotransferrin (unbound)

30
Q

when is transferrin reduced?

A

iron deficiency

anaemia of chronic disease

31
Q

when is transferrin increased?

A

genetic haemachromatosis and iron overload

32
Q

what is the role of ferritin?

A

iron storage

33
Q

what is the structure of ferritin?

A

Large spherical intracellular protein (450kDa)

34
Q

what does serum ferritin measure?

A

indirect measure of storage iron

35
Q

when is ferritin low?

A

iron deficiency

36
Q

when is ferritin raised?

A

iron overload

inflammation

37
Q

what are the disorders of iron metabolism?

A

iron deficiency
Iron malutilisation
Iron overload

38
Q

what is primary iron overload?

A

long term excess iron absorption with parenchymal rather than macrophage iron loading

39
Q

what is the cause of primary iron overload?

A

Hereditary haemochromatosis

40
Q

what is the cause of hereditary haemochromatosis?

A

Mutations of HFE gene

 Mutations of other iron regulatory proteins e.g. transferrin receptor, hepcidin, ferroportin very rare

41
Q

what is the pathophysiology of hereditary haemocromatosis?

A

o Decreases synthesis of hepcidin
o Increased iron absorption
o Results in gradual iron accumulation with risk of end organ damage

42
Q

what are the clinical features of hereditary haemocromatosis?

A

Weakness/fatigue, Joint pains, Impotence, Arthritis, Cirrhosis, Diabetes, Cardiomyopathy, Presentation middle age and later, Iron overload > 5g

43
Q

how is hereditary hemochromatosis diagnosed?

A

Genetics
transferrin saturation >50%
serum ferritin >300 g/l in men or >200 g/l in pre-menopausal women
Liver biopsy

44
Q

what is the management of hereditary haemochromatosis?

A

Weekly venesection = - 450-500ml, - 200-250mg iron
Initial aim to exhaust iron stores (ferritin <20 µg/l)‏
Thereafter keep ferritin below 50 µg/l
Family Screening

45
Q

what are the complications of hereditary haemochromatosis?

A 
Diabetes (BRONZE DIABETICS)
Infection
Cardiac failure
Hepatic failure/bleeding varices
hepatoma
46
Q

what are the causes of secondary iron overload?

A

o Transfusional

o Iron loading anaemias

47
Q

what are the sources of iron loading anaemias?

A
  • Repeated red cell transfusions

* Excessive iron absorption related to over-active erythropoiesis

48
Q

what are the disorders of iron loading anaemia?

A

Massive ineffective erythropoiesis
o Thalassaemia syndromes
o Sideroblastic anaemias

49
Q

what are the refractory hypoplastic anaemias that can cause iron loading anaemia?

A
  • Red cell aplasia

* Myelodysplasia (MDS)

50
Q

what is the management of secondary iron overload?

A

No venesection

Iron chelating agents: Desferrioxamine, Deferiprone and Deferasirox

Haematology (13 decks)

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