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Haematology > Erythropoiesis > Flashcards

Erythropoiesis Flashcards

1
Q

What engulfs old RBCs?

A

Phagocytic cells of the liver and spleen

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2
Q

What are globular haemoglobin proteins broken down into after RBC break down?

A 
Amino acids which enter the blood stream
Haem group (minus iron) is converted to bilirubin
Bilirubin is transported to liver and secreted into bile
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3
Q

What happens to iron after RBC breakdown?

A

Finds to transferrin in the blood and is recycled

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4
Q

What is erythrocyte production regulated by?

A

Erythropoietin (EPO)

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5
Q

Where is EPO released from?

A

Kidney

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6
Q

What is the process from myeloid stem cell to mature erythrocyte?

A

Proerythroblast (derived from myeloid stem cells)
Polychromatic erythroblast (Hb in cytoplasm)
Orthochromatic erythroblast (Nucleus shrinks, full complement of Hb in cytoplasm)
Erythroblast excludes nucleus
Reticulocyte into circulation
Mature erythrocyte

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7
Q

What is the shape of RBCs described as?

A

Biconcave disc

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8
Q

What are the approximate sizes of RBCs?

A

8 (micro)m diameter
2 (micro)m thick at edge
1 (micro)m thick in centre

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9
Q

What % of blood is plasma?

A

55%

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10
Q

What % of blood is the buffy coat and what is its constituents?

A

1%

Platelets and WBCs

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11
Q

What is haematocrit?

A

% RBCs

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12
Q

What makes up packed cell volume?

A

Everything but plasma

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13
Q

What regulates RBC ion balance volume?

A

Sodium pump

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14
Q

How is ATP synthesised in RBCs?

A

Anaerobic glycolysis

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15
Q

What helps keep iron in Fe2+ state?

A

NADH from glycolysis

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16
Q

What is partly metabolised through a hexose monophosphate shunt, and what does this shunt do?

A

Glucose

Produces NADPH, required for maintenance of adequate levels of reduced glutathione

17
Q

What is produced when PO2 is reduced?

A

2,3 biphosphoglycerate- releases O2 from Hb

18
Q

What is glutathione?

A

Tripeptide, consisting of glutamate, cysteine and glycine

19
Q

What does glutathione do?

A

Reduced glutathione (it’s normal state) combats oxidative stress

20
Q

What are ROS?

A

Free radicals- highly reactive molecules with unpaired electrons

21
Q

What does excessive free radicals or inadequate antioxidant defence mechanisms lead to?

A

Damage of cellular structures and enzymes

22
Q

What does glutathione protect against?

A

Toxic effects of ROS

Also essential to detoxify hydrogen peroxide, the primary intermediate in oxidative damage

23
Q

What can glucose 6-phosphate dehydrogenase insufficiency cause?

A

NADPH deficiency, leading to reduced glutathione, leading to cell damage

24
Q

What 3 forms is CO2 produced by tissues carried to the lungs in?

A

Physically dissolved in solution (10%)
Bound to Hb-carbamino-haemoglobin (30%)
As bicarbonate ion (60%)

25
Q

What is CO2 transport facilitated by?

A

Carbonic anhydrase

26
Q

What happens in the Cl- shift?

A

Chloride/bicarb exchange- exports HCO3- (facilitated diffusion)
Cl- enters to preserve cell potential

27
Q

What is the structure of Adult Hb?

A

4 globin sub units, each containing a single haem molecule
Haem group contains single Fe2+ ion
Each haem group can bind one O2 molecule

28
Q

When fully saturated, how much O2 will 1g Hb bind?

A

1.34ml

29
Q

What is required for Hb synthesis?

A

Synthesis of globin chains- 4 per molecule of Hb
Synthesis of porphyrin ring (haem group)
Insertion of iron into haem

30
Q

What globin sub units make up adult and foetal Hb?

A

HbF- predominantly a2y2, in late gestation y expression falls, B expression rises
HbA- predominantly a2B2

31
Q

Do allosteric interactions (e.g. O2 binding to Hb) follow Michaelis-Menten kinetics?

A

No

32
Q

What does increasing substrate concentration in allosteric interactions result in?

A

Sigmoidal curve rather than hyperbola, indicating co-operative behavior

33
Q

What is co-operativity in allosteric interactions?

A

The influence that the binding of a ligand to one site on the molecule has on the binding of ligand to a different functional site

34
Q

Describe the Hb dissociation curve in terms of arterial and venous blood

A

Arterial- plateau phase sustains SaO2 >90% over wide range of inspired (blood) pO2
Venous- steep phase of curve favours O2 offloading to tissues

35
Q

Does HbF have a higher affinity for O2 and 2,3 BPG than HbA?

A

Higher for O2, lower for 2,3 BPG

This facilitates the transfer of O2 from mother to foetus

Haematology (23 decks)

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