Normal erythropoiesis

Question 1

describe properties of mature RBC

Answer 1

No nucleus or mitochondria
No DNA/RNA, therefore no cell division
Short-lived
life span ~ 120 days

Question 2

what is the stimulus for EPO production

Answer 2

low oxygen supply to kidney

Question 3

What are the stages of erythropoiesis

Answer 3

proerythroblast (derived from myeloid stem cells)
polychromatic erythroblast (Hb appears in cytoplasm)
orthochromatic erythroblast (nucleus shrinks, full complement of Hb in cytoplasm)
erythroblast extrudes nucleus
reticulocyte into circulation

Question 4

describe form and function of RBC

Answer 4

Diffusion distance minimised
Surface to volume ratio maximised
Flexible membrane
can deform to allow cells to squeeze in single file through capillaries

Question 5

How is ATP produced in RBC

Answer 5

Glycolysis

Question 6

What is the purpose of 2,3 BPG

Answer 6

it is produced at low pO2 and reduces the affinity of Hb to O2

Question 7

what reduces glutothion

Answer 7

NADPH

Question 8

What is the function of Glutothione within the cell

In what condition is there are reduction in Glutothione

Answer 8

Glutathione helps protect against the toxic effects of reactive oxygen species (free radicals)

(Reduced) glutathione is essential to detoxify hydrogen peroxide (H2O2), the primary intermediate in oxidative damage

NADPH from the pentose phosphate pathway is needed to produce reduced glutathione

In RBCs, lack of reduced glutathione (e.g. as a consequence of glucose 6-phosphate dehydrogenase insufficiency and hence NADPH deficiency) can lead to cell damage

Question 9

What happens when there is an inability to maintain a reduced form of glutathione within the cell

Answer 9

The inability to maintain reduced glutathione in RBCs leads to increased accumulation of peroxides, predominantly H2O2, that in turn results in a weakening of the cell wall and concomitant haemolysis. Accumulation of H2O2 also leads to increased rates of oxidation of haemoglobin (Fe2+) to methaemoglobin (Fe3+) that also weakens the cell wall.

Question 10

How is CO2 transported within the blood

Answer 10

Physically dissolved in solution (amount  Pco2)
approx. 10 % of total CO2
Bound to Hb – carbamino-haemoglobin
approx. 30 % of total CO2
As bicarbonate ion – HCO3-
approx. 60 % of total CO2

Question 11

describe the reaction of CO2 and H2O to Produce Biacarbonate and H+

Answer 11

CO2 + H2O  H2CO3  H+ + HCO3-

carbonic anhydrase is the enzyme that facilitates reaction

H+ binds to deoxygenated Haemoglobin

Bicarbonate exits the cell in exchange for Cl-

reaction is reversed at lungs

Question 12

what are the normal concetrations of haemaglobin

Answer 12

♂ 130 – 180 g/l

♀ 115 – 165 g/l

Question 13

what are the physiological benefits of the haemoglobin dissociation curve

Answer 13

Arterial – Plateau phase sustains SaO2 >90% over wide range of inspired (blood) pO2

Venous – steep phase of curve favours O2 off-loading to tissues