Transport of CO2 Flashcards
3 means of transporting CO2 backt ot he lungs
5% dissolved in blood plasma
10% combined with haemoglobin to give carbamino-haemoglobin
85% transported as hydrogen carbonate ions (HCO3^-)
What reaction occurs when CO2 diffuses into the RBC cytoplasm
CO2+H2O》H2CO3
What ions does carbonic acid (HCO3) dissociate into when aqueous in the cytoplasm
HCO3^- and H^+
What enzyme catalyses the formation of carbonic acid in RBC
carbonic anhydrase
Why does carbonic acid so quickly dissociate
Bc it is unstable (easily decomposes)
What happens to HCO3^- ions following their production
They diffuse out of the RBC into the blood plasma down conc grad
Chloride shift?
Cl^- ions diffuse into the RBC to replace the HCO3^- ions that have left. This is to maintain electrochemical neutrality in the RBC
What affect would excessive H+ ions have on the cell
Lower pH, reduce enzyme activity by causing inactivation/ denaturation
What affect do H^+ ions have on oxyhaemoglobin
H+ decreases Hb affinity for O2
Benefit of having Hb (rather than oxyhaemoglobin) in the cell?
HB acts as a BUFFER
Binds to H^+ ions to form haemoglobinic acid
Symbol for haemoglobinic acid
HHb
How does the production of HCO3^- ions account for the Bohr effect? 4
H+ ions decrease Hb’s affinity for O2 so O2 is MORE READILY dissociated
H+ ions combine with Hb to give HHb
H+ ions have displaced the O2 molecules
So more O2 is dissociated at a high CO2 conc
What are the benefits of the H+ ions binding to the Hb from Hb.4O2 x2
Stops the lowering of the cell pH
Causes the dissociation of oxygen molecules so they can diffuse out of the RBC into the tissue fluid then into cells for use
name for HCO3^- ions
Bicarbonate ions/ hydrogen carbonate ions
name for HCO3^- ions
Bicarbonate ions
Name for HCO3
Ccarbonic acid
How does this info explain Bohr shift
This is the reasoning as to why increased CO2 conc causes oxyhaemoglobin to dissociate its O2 at lower ppO2 than it would typically (left shifted curve on graph)
Why is Hb said to be a buffer in the RBC
It keeps the pH of the cell constant (prevents it from decreasing) by binding to the dissociate H+ ions from the carbonic acid profuced
