s4. CO2 in blood Flashcards
what range should arterial blood pH be kept in?
7.35-7.45
what is a buffer
compounds which are able to bind or release H+> accept/ donate > to maintain pH in narrow range
what is the reaction for the bicarbonate buffer system?
CO2 + H20 H2CO3 H+ + HCO3-
Equation to work out dissolved conc of CO2
solubility constant x pCO2
solubility constant= 0.23mmol/L/kPa
what is the law of mass action?
the rate of the reaction depends on the amounts of reactants and products
(reversible reaction)
apply the Henderson-Hasselbalch eq to the /co2-Bicarb buffer system
pH= pKa + log ([HCO3-] /[pCO2] x 0.23)
what is the ideal ratio of bicarbonate to dissolved CO2
21 (20:1)
plasma pH depends on?
- conc dissolved CO2 (controlled by breathing rate)
- conc of bicarbonate (controlled by kidneys)
- ratio of [HCO3-]:[CO2]
why is out body pH slightly alkaline?
7.4
bicarb co2 buffer is favoured slightly to producing H+ and HCO3-
what is the relationship between CO2 and pH
when CO2 inc, pH dec
which enzyme is involved in bicarbonate production in RBC?
what happens to the products?
Carbonic Anhydrase
CO2+H20–> HCO3- + H+
produced HCO3- is transported out of RBC by chloride:bicarbonate exchanger
the H+ that is also produced by the reaction is bound to haemoglobin
what is the importance of H+ binding to haemoglobin when produced in RBCs from bicarbonate production reaction?
if H+ did not bind to Hb, the reaction you;d be pushed in the opposite direction, meaning bicarbonate is used up NOT produced.
> Hb acts as a buffer
- deoxy haemorrhage is the best at binding H+!!
what controls HCO3- concentration?
kidney
made in RBC, CONTROLLEd by kidney
what happens in regards to bicarbonate buffer system when extra acid is produced as part of normal metabolism?
- acids react with HCO3- to produce CO2
- CO2 levels inc, pH dec > acidotic
- plasma bicarbonate store falls
> extra CO2 produced is removed by breathing and pH changes are buffered.
more bicarb produced to replenish buffers
compare the amount of H+ ions that bind to Hb at lungs vs at tissues
- relate this to CO2 and carbamino compounds
at lungs:
Relaxed state Hb (more O2 binds Hb) > less H+ bind
tissues:
Tense state Hb (less O2 binds Hb) > more H+ bind
*same principal with CO2 in carbamino compounds
