Pathology L06 Red blood cells Flashcards
What are RBCs unable to do since they lack mitochondria and ribosomes?
incapable of both oxidative phosphorylation and protein synthesis
What is the diameter or a RBC?
7-8um
What are 3 functions of Hb?
Oxygen transport (main), carbon dioxide transport (10% of CO2 from tissue to lungs) and NO transport
What chromosome are the alpha and beta globin genes found on?
16 and 11 respectively
What is haemoglobin switching?
The sequential expression of embryonic, fetal and adult haemoglobin in the developing erythroblast during ontogeny
What makes O2 binding to Hb co-operative?
Binding of each oxygen enhances binding of the next - Bohr effect
What 3 changes can cause a lower O2 affinity?
reduced pH, increased temp and increased 2,3 BPG
What is the advantage of HbF not being able to bind 2,3 BPG effectively?
HbF has a higher affinity than HbA for oxygen. Oxygen is preferentially loaded onto HbF in fetal blood from HbA in the mother’s blood
What are the 2 pathways for glucose metabolism in the RBC?
Glycolysis and Hexose monophosphate shunt (pentose phosphate pathway)
What is the purpose of the reducing power generated by the HMP shunt?
Countering any potential reactive oxygen species that may form from the oxygen carried (OH-, H2O2, HO2, O2-) and the damage to lipids, proteins and enzyme cofactors they would produce. It does this by producing NADP/H and Glutathione
What is methaemoglobin?
An oxidise form of Hb with Fe3+ instead of Fe2+. It cannot carry oxygen and precipitates out.
What is the enzyme converting glucose 6P to 6P gluconate?
glucose 6P dehydrogenase
How does HMP shunt prevent oxidative stress?
Production of large amounts of NADPH that prevents oxidative stress by maintaining glutathione levels. Glutathione is a reducing agent that converts peroxide to water and prevents oxidative damage.
In patients with G6PD deficiency, what oxidising agents may trigger oxidative stress?
medications, broadbeans and infections
What might the anaemia from pyruvate kinase deficiency (most common glycolytic enzyme deficiency) not be as symptomatic as expected?
PK def causes loss of membrane pump function and loss of membrane plasticity, leading to usually shaped cells that are destroyed in the spleen. There is also an increase in 2,3-DPG, shifting the haemoglobin curve to the right, allowing greater offloading of oxygen. As a result, only appear slightly anaemic.
