Carbon Dioxide In Blood

Question 0

Write the Henderson-Hasselbalch equation, and be able to calculate the plasma pH given the pCO2 and [HCO3-]

Answer 0

pH = pK + log([HCO3-]/(pCO2 x 0.23) ) 
(pK = 6.1)

Question 1

List the reactions of CO2 in blood

Answer 1

CO2 more soluble than O2 –> reacts with water (controls pH) in RBCs
CO2 + H2O HCO3- + H+

Question 2

State the factors influencing the hydrogen carbonate concentration of plasma

Answer 2

Kidneys - creation/excretion

Question 3

Describe the buffering action of Hb in red blood cells

Answer 3

H+ binds to RBCs –> more CO2 reacts –> increased HCO3-

HCO3- leaves RBC in exchange for Cl-, forming 25mmol/L in plasma

Question 4

Describe the function of carbamino compounds

Answer 4

CO2 + amino acid/protein

Carbamino compounds facilitate transport of CO2 (11%)

Question 5

State the normal content of CO2 in arterial and venous blood

Answer 5

Arterial CO2 = 21.5mmol/L

Venous CO2 = 23.5mmol/L

Question 6

Describe the process of transport of CO2 from tissues to lungs and state the proportion of CO2 travelling in various forms

Answer 6

HCO3- = 80%
Carbamino = 11% 
Dissolved = 8%