Canonical Question
Gas Transport – Oxygen
Master answer
Carbon Dioxide
Total CO2 in arterial blood: 480ml/L
Total CO2 in venous blood: 520ml/L
Oxygen
CaO2 = (1.34 x [Hb] x SpO2) + 0.03 paO2
= 200ml/L
Approx 150ml/L in venous blood
Carried in 4 forms:
Carried in 2 forms:
| Dissolved CO2 CO2 has 20 times solubility compared with O2 PaCO2 ~40mmHg PvCO2 ~46mmHg | Dissolved O2 Minor component According to Henry’s law: – Dissolved O2 proportional to partial pressure of O2 in gas phase. – Solubility coefficient 0.24 PaO2 ~100mmHg PvO2 ~45mmHg |
| Carbamino compounds Minor component of CO2 carriage in blood, however 30% of the A-V difference in CO2 carriage Hb is major protein for CO2 carriage Reduced Hb has 3.5x CO2 binding capacity and this is the major factor for the Haldane Effect Haldane effect Increased CO2 carrying capacity in deoxygenated blood – Due to increased buffering capacity of reduced Hb | Haemoglobin bound O2 Major component of O2 carriage According to oxyhaemoglobin dissociation curve Curve altered by pH, pCO2 and 2,3 BPG – Right shift (decreased affinity) due to increased CO2 and 2,3 BPG – Left shift (increased affinity) due to increased pH – CO2 effect on Hb is the Bohr Effect: In presence of CO2, there is decreased oxygen carrying capacity in blood |
| Bicarbonate Major component of CO2 carriage in blood | – |
| Carbonic acid Negligible | – |
Sakurai 2016
Exam appearances
| Exam | Exact wording | Relationship | Success |
|---|---|---|---|
| 2012B Q01 | Compare and contrast the carriage of oxygen and carbon dioxide in blood. | historical_member | — |
| 2024A Q11 | Compare and contrast the carriage of oxygen in the blood with the carriage of carbon dioxide. | historical_member | — |