Normal Erythropoiesis Flashcards
What do RBCs contain to carry oxygen?
Haemoglobin - high oncotic pressure, oxygen rich environment (oxidation risk)
Do RBCs contain mitochondria?
No - limited to glycolysis for energy generation (no Kreb’s cycle)
RBCs do not have a nucleus, what does this allow for?
Makes it more deformable, and more room for Hb molecules
Can’t divide, can’t replace damaged proteins - limited cell lifespan
Why do RBCs have a high surface area / volume ratio?
Allow for gas exchange
Need to keep water out
Why is it important that RBCs are flexible?
To squeeze through capillaries - specialised membrane required that can go wrong
Describe the membrane of RBCs
Why do RBCs need energy?
To maintain specific ion concentrations gradient and keep water out
The sodium potassium pump keeps ion concentrations right
Keeps system working in cell
Keeps water out
But it needs ATP (Energy)
Describe the structure of haemoglobin
Tetrameric globular protein
HbA (adult) has 2 alpha and 2 beta chains
Heme group is Fe2+ in a flat porphyrin ring
One heme per subgroup
One oxygen molecule binds to one Fe2+ (oxygen does not bind to Fe3+)
What is the function of haemoglobin?
Deliver oxygen to the tissues
Act as a buffer for H+
CO2 transport
Where does red blood cell production occur?
In the bone marrow as a result of proliferation and differentiation of HSCs
Describe the pathway by which erythropoietin stimulates RBC production
Where does red cell destruction occur?
In spleen (and liver)
What is the average red cell lifespan?
120 days
Aged red cells are taken up by?
Macrophages - taken out of circulation
Red cell contents are recycled
Globin chains are recycled to what?
Amino acids
Heme group is broken down to?
Iron and bilirubin
Bilirubin is taken to?
Liver and conjugated - then excreted in bile (colours faeces and urine)
Describe the pathway of breaking down heme to bilirubin
Oxygen free radicals are easily made as there is a lot of oxygen in blood. Why are free radicals dangerous for RBCs?
Free radicals are dangerous
Can oxidise Fe2+ to Fe3+ which doesn’t transport oxygen
Free radicals damage proteins ~(remember we can’t repair/replace proteins as no machinery to do so -so once they’re damaged that’s it)
What does a red blood cell need?
Describe this diagram
What are examples of reactive oxygen species?
Superoxide
Hydrogen peroxide
These are free radicals and have unpaired free electrons
Capable of interacting with other molecules (proteins, DNA) and damaging their structure
What is glutathione?
Protects us from hydrogen peroxide by reacting with it to form water and an oxidised glutathione product (GSSG) -> maintains redox balance
How can glutathione be replenished?
By NADPH which in turn is generated by the hexose monophosphate shunt
