Erythropoiesis Flashcards
Properties of mature RBCs
packed with Hb
no nucleus or mitochondria
no DNA/RNA - no cell division
Life span of a RBC
120 days
which organ removed fragile old RBCs from circulation
the spleen
where are new cells produced
red bone marrow
what are new RBCs produced from
pluripotent stem cells
what are RBCs broken down to
globular haemoglobin proteins are broken down to amino acids
Haem group is converted to bilirubin
Iron binds to transferrin in the blood and is recycled
where does bilirubin go
transported to the liver and secreted into bile
it’s breakdown products colour urine and faeces
what regulates erythrocyte production
EPO- erythropoietin, released by the kidneys
what causes the kidney to release EPO
hypoxia
steps of erythropoiesis
- pro erythroblast (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
- mature erythrocyte
structure of a RBC and its importance
Biconcave disc:
- increased surface area
- Flexible membrane so that cells can squeeze through capillaries in single file
- decreased diffusion distance
what is the largest component of blood
plasma (55%)
what % of blood composition do platelets + white blood cells make up
1%
what % of blood is made up of RBCs in males, and in females
males- 40-50%
famles- 36-46%
what is haematocrit
the volume of RBCs as a % of total blood volume
how is RBC ion balance and cell volume regulated
Na+/K+ ATPases (the sodium pump) energy dependent process
through what route does a RBC synthesise ATP
Anaerobic glycolysis (no mitochondria in RBC so cannot do aerobic glycolysis)
what component from glycolysis keeps iron in Fe2+ state
NADH
what is produced when Oxygen is low in order to release oxygen from haemoglobin
2,3 biphosphoglycerate
what is glutathione
tripeptide consisting of glutamate, cysteine and glycine
what other mechanism is some glucose metabolised through
hexose monophosphate shunt
another name for the hexose monophosphate shunt
pentose phosphate pathway
what does the pentose phosphate pawthay produce
nucleic acids and NADPH
role of glutathione
combats oxidative stress (i.e. it is an anti-oxidant)
what are free radicals
highly reactive molecules with unpaired electrons
what happens if there is excessive free radicals or inadequate antioxidant defence mechanisms?
damage of cellular structures and enzymes
what is the importance of glutathione
helps protect against the toxic effects of free radicals
essential to de-toxify hydrogen peroxide
what is needed to produce glutathione
NADPH from pentose phosphate pathway
which condition causes a lack of glutathione
glucose 6-phosphate dehydrogenase deficiency
which form of glutathione acts as an anti-oxidant
the reduced form
how is CO2 carried to the lungs
- dissolved in solution
- bound to Hb (carbamino-haemoglobin)
- as bicarbonate (60%)
how is the movement of CO2 facilitated
by carbonic anhydrase
what is haemoglobin comprised of
4 globin (protein) sub-units, each containing a single haem molecule
what does each haem molecule contain
single Fe2+ Ion
porphyrin ring
what can each haem group bind to
one O2 molecule
what does haemoglobin synthesis require
synthesis of globin chains- 4 per molecule of Hb
synthesis of porphyrin ring (haem group)
insertion of Fe2+ into haem
normal Hb concentration for male and females
male- 130-180 g/l
female- 115-165 g/l
differences between fetal and adult Hb
fetal Hb has a higher affinity for O2
has a lower affinity for 2,3 BPG
Facilitates the transfer of O2 from the mother to the foetus
factors that shift the oxygen haemoglobin curve to the right
Increased 2,3 DIphosphoglycerate, increased temperature, increased H+
what does a shift to the right mean
more oxygen released at tissues
what pathway generates 2,3 diphosphoglycerate
Rapapoport-Lubering Shunt
name of the pathway that generates ATP and NADH by anaerobic glycolysis
Embden-Myerhof pathway
