red blood cells Flashcards
what does haemoglobin do? 3
- binds to oxygen in the lungs where PO2 is high
- unbinds in tissues (where Po2 is low)
- must be weak enough to be reversible
what mechanisms reduce oxygen affinity?
cooperativity
right shifting of the binding curve
what does each subunit of haemoglobin have? 5 how many subunits?
- small haem group
- coloured red/blue
- contains an iron atom- binding site of the oxygen
- 2D rigid structure
- porphyrin ring
-4
explain cooperativity? 4
- each subunit can carry 1 oxygen molecule on its haem
- each subunit influences its neighbours
- if one binds, so do the others
- if one releases, so do the others
what are the two main types of haemoglobin?
their subunits
where they are found
-HbA
in healthy adults
2 alpha and 2 beta (tetramer)
maternal haemoglobin
-HbF 2 alpha, 2 gamma adults have a small percentage binds to oxygen more strongly foetal haemoglobin
what is the bohr effect? 4
- increased blood carbon dioxide leads to decreases affinity for oxygen
- decrease in blood pH leads to decrease in affinity for oxygen
- increase in blood and carbon dioxide lead to decreases in blood pH
- CO2 and H+ bind to Hb but at different sites to O2
how can carbon dioxide be transported? 3
- 10% in blood plasma
- 22% as carbamino (natural substance in the blood)
- 68% as HCO3- (bicarbonate)
what is the chloride shift?
- more Cl- inside the RBCs in venous blood than arterial
what is pO2
partial pressure of oxygen
when comparing the graph of fractional saturation against partial pressure of oxygen for myoglobin and haemoglobin what do they curves look like?
- Hb= sigmoidal (s shaped) implies cooperativity
- myoglobin= hyperbolic implies small amounts of oxygen fill the myoglobin until it cannot hold anymore
what can lead to a rightward shift of oxygen affinity? 4 what is a rightward shift?
- decrease in affinity for oxygen
- co2
- H+
- CL-
- 2,3 DPG
what is 2,3 DPG?
what does it do?
diphospho-glycerate
-binds to Hb
tiny compared to Hb
-lowers affinity of Hb for O2
-HbF has a low affinity for 2,3 DPG compared to maternal blood, so HbF has a higher affinity for oxygen
what happens in active muscles? 9
- oxygen is low
- carbon dioxide is high
- blood is slightly acidic due to lactic acid and CO2
- temp is higher
- myoglobin is present
- as blood runs along capillary, oxygen leaves Hb (cooperativity)
- CO2 and H+ bind to the Hb shifting the Hb saturation right
- HCO3- leaves the RBC into the plasma
- CK_ leaves the plasma and enters the RBC (CL- shift)
how is breathing controlled by o2, co2 and H+? 5
- plasma o2 must drop a lot before respiratory drive increases
- main driver to increase respiratory rate is H+ in the CSF
- H+ is slow to get to the CSF, but CO2 can get in
- once CO2 is in the CSF it makes carbonic acid and H+
- medullary receptors sample from the interstitial fluid and CSF fluid
what is the structure of a erythrocyte? 7
- definitive= mature
- biconcave disc
- anucleate
- no organelles
- 7 micrometres diameter, 2 micrometers height
- contain haemoglobin
- red when oxygenated out of body
