Lecture 1: RBCs Flashcards
Where does oxygen bind haemoglobin?
Binds the iron ions in the haem (4 in every Hb - 1 per subunit)
How much more oxygen is carried on Hb compared to plasma?
70X
What is the equation for oxidative respiration?
C6H12O6 + 6O2 –> 6CO2 + 6H2O + 36ATP
What is the equations for anaerobic glycolysis?
C6H12O6 –> 2 lactate + 2ATP
How big is the small haem group in Hb?
616Da
How big is the large globin peptide in Hb?
17000Da
Describe HbA
2 alpha + 2 beta subunits
Describe HbF
2 alpha + 2 gamma subunits
Binds O2 more strongly than HbA
Adults have a small percentage of HbF
What is the Bohr effect?
Increase blood CO2 –> decrease affinity of Hb for O2
Decrease blood pH –> decrease affinity of Hb for O2
Because..
Increase blood Co2 –> decreases blood pH
CO2 and H+ bind Hb but in different place to O2
What are the percentages of CO2 transport in blood?
Dissolved - 10%
Carbamino - 22%
HCO3- - 68%
Describe the chloride shift for RBCs
CO2 + H2O –> H2CO3 + H+
The H+ goes on to bind Hb- to make HHb
The HCO3- leaves the RBC via an exchanger that brings Cl- into the RBC
More Cl- inside the RBCs in venous blood than arterial blood
Describe O2 binding curves of Hb and myoglobin
Myoglobin - hyperbolic
Hb - sigmoidal
What things cause rightward shift?
Rightward shift –> decreases affinity for O2
CO2, H+, Cl-, 2,3-DPG
What is 2,3-DPG?
Binds to Hb, lowers the affinity of Hb for O2, found in erythrocytes at 5mM
Foetal HbF has higher affinity for O2 than HbA
What happens in active muscles?
- O2 leaves the Hb (cooperativity)
- CO2 and H+ bind to Hb – shifts Hb saturation to right
- HCO3- leaves RBC plasma
- Cl- leaves plasma enters RBC (Cl- shift)
What is the main driver to increase respiratory rate?
H+ in CSF
How big are erythrocytes?
7uM by 2uM
What cells are in 1ul of blood?
RBCs - 5million
Leukocytes - 9000
Platelets - 300,000
Reference range of packed cell volume
M- 40-52%
F- 36-48%
Reference range of Hb
M- 13-17g/dL
F- 12-16g/dL
Reference range for Mean Cell Haemoglobin (MCH)
27-34pg
Reference range for Mean Corpuscular Volumes (MCV)
80-100fL
Erythropoiesis process
Haematopoetic stem cell –> BFU-E –> CFU-E –> erythroblasts (all these stages are erythropoietin dependent)
Erythroblasts –> reticulocytes (iron dependent)
Reticulocytes –> erythrocytes
What is methaemoglobinaemia?
Fe in Hb is Fe3+ (oxidised) instead of the usual ferrous Fe2+
How much stronger is COs affinity Hb compared to O2?
250%
What is the treatment for CO poisoning?
95% O2 / 5% CO2 (CO2 drives the CO out of the binding pocket so O2 can bind)
What are the types of polycythaemia?
Increased number of RBCs
Physiologic - due to living at high altitude
Polycythaemia vera - neoplasm, no cure, venesection