Transport of O2 and CO2 in the blood Flashcards
Why does efficient transport of oxygen in the blood require a carrier?
Oxygen has a very low solubility in water
Why does Hb allow 4x more oxygen to be transported than we need at rest?
To allow an overshoot during exercise
What subunits make up Hb?
2 alpha and 2 beta subunits
What is the difference in structure of foetal Hb and what effect does this have?
Foetal Hb contains 2 gamma instead of 2 beta subunits. This causes it to have a higher affinity fro oxygen - so can bind oxygen at lower partial pressure
What happens to the affinity for oxygen in sickle cell anaemia?
Hb in the RBCs have a lower affinity for oxygen so cannot bind as well - needs a higher partial pressure
Why are sickle cells classified as less stress resistant than healthy RBCs?
They are more venerable to deformation during passage through the capillaries to are degraded much quicker
What affect do sex hormones have on Hb concentration?
Oestrogen causes vasodilation
Androgens cause vasoconstriction
What affect does vasoconstriction have on Hb concentration?
Reduced blood flow, so there is a need to increase the carrying capacity of oxygen so Hb content is increased.
What affect does vasoconstriction have on Hb concentration?
Increased blood flow reduces the need to increase the carrying capacity of oxygen so Hb content is decreased
Where on Hb does oxygen bind?
To the harm group via Fe atom
Where on Hb does CO2 bind?
N-terminus
Why is CO toxic?
CO and O2 compete for the same binding site and CO outcompetes O2 and binds irreversibly so O2 cannot eb transported
Why is it a sigmoidal curve?
The binding of the 1st oxygen is hard but this causes a conformational change that helps the next ones bind.
When the limit is nearly reached very little additional binding occurs so the curve flattens out (even with a large increase in partial pressure)
What is the effect of shifting the curve to the right?
When might this occur?
Decreased affinity for oxygen
Needs higher partial pressure to bind.
Occurs when increasing CO2 concentration
Why does an increase in CO2 decrease Hb affinity for oxygen? What is this called?
More CO2 means more H2CO3, so more H+ so Hb undergoes a conformational change and can’t bind oxygen as well. Bohr effect
What is the effect of increasing temperature on the oxygen dissociation curve?
Shifts to the right
Lower affinity for oxygen as it denatures Hb
When and where is 2,3DPG produced
In erythrocytes during glycolysis (anaerobic respiration)
When O2 concentration is low
What is the affect of 2,3 DPG on oxygen and the dissociation curve?
It promotes the release of oxygen from Hb because oxygen concentration is low this shifts the curve to the right so less oxygen binds.
Why does foetal Hb need a higher affinity for oxygen?
It competes with the mothers supply of oxygen
Why does foetal Hb have a higher affinity for oxygen structurally?
It has a lower affinity for 2,3 DPG so it cannot promote the release of oxygen
What enzyme is involved in the transport of CO2?
Carbonic anhydrase
How is CO2 transporter in the blood in proportions?
23% bound to Hb
7% free in the blood
70% as carbonic acid
What is chloride shift?
H+ and HCO3- produced from carbonic acid.
H+ is buffered by Hb
HCO2- transported to plasma and replaced by Cl- to maintain neural charge
