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Fundamentals in Pathology > Haemoglobin structure and function > Flashcards

Haemoglobin structure and function Flashcards

1
Q

What is the structure of haemoglobin? [3 marks]

A
  • Globular haemoglobin
  • Contains haem as a prosthetic group
  • Haem is a complex of protoporphyrin IX and Fe2+
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2
Q

How does iron fit into haem? [1 mark]

A

It is held in the centre of the haem molecule by coordinate bonds to 4 nitrogens in a porphyrin ring.

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3
Q

Does haem and globin synthesis occur in the same place? [1 mark]

A

NO - they occur separately

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4
Q

Where is haemoglobin synthesised? [2 marks]

A
  • 65% in erythroblasts

- 35% in reticulocytes

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5
Q

What happens in kidneys in hypoxia? [2 marks]

A
  • Kidneys increase production of erythropoietin.

- This increases erythrocytes and haemoglobin synthesis.

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6
Q

Where is haem synthesised? [1 mark]

A

In mitochondria

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7
Q

How haem synthesised? [3 marks]

A
  • Transferrin carries iron to the transferrin receptor of a reticulocyte.
  • Protoporpyrins are synthesised (mediated by EPO and vit. B6)
  • Protoporphyrin + iron = haem
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8
Q

What is the rate limiting enzyme in haem synthesis? [1 mark]

A

Ala-synthase

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9
Q

Where does globin synthesis occur? [1 mark]

A

Polyribosomes

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10
Q

What is thalassaemia caused by? [1 mark]

A

Reduced rate of synthesis of normal α or β chain.

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11
Q

Which chromosome are the B-cluster (β, γ, δ and ε globin) genes found in? [1 mark]

A

Chromosome 11 (in its short arm)

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12
Q

Which chromosome are the Α-cluster (α and ζ globin) genes found in? [1 mark]

A

Chromosome 16 (in its short arm)

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13
Q

What are the forms of embryonic haemoglobin? [3 marks]

A
  • Gower I (ζ2ε2)
  • Gower II (α2ε2)
  • Portland (ζ2γ2)
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14
Q

What is foetal haemoglobin? [1 mark]

A

α2γ2

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15
Q

What are the forms of adult haemoglobin? [3 marks]

A
  • HbA (α2β2): makes up 96-98% of blood
  • HbA2 (α2δ2): makes up 1.5-3.2% of blood
  • HbF (α2γ2): makes up 0.5-0.8% of gene
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16
Q

What are the functions of haemoglobin? [3 marks]

A
  • Carrying oxygen from lungs to tissue
  • Removing CO2
  • Buffering action, maintains pH by changing from oxyhaemoglobin to deoxyhaemoglobin
17
Q

How many molecules of oxygen can haemoglobin bind to? [1 mark]

A

4

18
Q

What happens to 2,3-diphosphoglycerate (2,3-DPG) when haemoglobin is oxygenated? {2 marks]

A
  • 2,3-DPG gets pushed out.

- β-chains move closer

19
Q

What happens to 2,3-diphosphoglycerate (2,3-DPG) when haemoglobin is deoxygenated? [3 marks]

A
  • β-chains get pulled apart
  • 2,3-DPG enters
  • There’s a lower affinity of haemoglobin to oxygen
20
Q

What happens if there’s more 2,3-DPG in the red blood cell? [1 mark]

A

More oxygen is released from the red blood cell to tissues

21
Q

What does the amount of oxygen bound to haemoglobin and released depend on? [3 marks]

A
  • PO2
  • PCO2
  • Affinity of haemoglobin for O2
22
Q

What is oxygen affinity and what does it determine? [2 marks]

A
  • The ease with which haemoglobin binds and releases oxygen

- It determines the proportion of O2 released to the tissues or loaded onto the cells at a given oxygen pressure

23
Q

What is the Bohr effect? [3 marks]

A
  • When there’s an increase in CO2 production and drop in blood pH.
  • Results in dissociation curve shifting to the right
  • O2 is released from haemoglobin
24
Q

What is P50? [1 mark]

A

The partial pressure of oxygen where Hb is 50% saturated.

25
Q

How does P50 affect haemoglobin’s affinity to oxygen? [2 marks]

A

LOW: increased affinity to O2
HIGH: decreased affinity to O2

26
Q

What does the normal position of the dissociation curve depend on? [4 marks]

A
  • Concentration of 2,3-DPG
  • Blood pH
  • CO2 in red blood cells
  • Structure of haemoglobin
27
Q

What are the standard conditions? [3 marks]

A
  • Temperature: 37 degrees Celsius
  • pH: 7.4
  • Base excess: 0
28
Q

What is base excess? [1 mark]

A

The amount of H+ required to keep blood pH at 7.4

Fundamentals in Pathology (11 decks)

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