The partial pressure of oxygen in the alveoli is $13.3\,\text{kPa}$. At this oxygen partial pressure, the total volume of oxygen carried by $100\,\text{cm}^3$ blood is $19.78\,\text{cm}^3$ at pH 7.4 and $37\,^\circ\text{C}$. The volume of oxygen that combines with haemoglobin at $13.3\,\text{kPa}$ is $19.48\,\text{cm}^3$ $100\,\text{cm}^{-3}$ blood. Calculate the percentage of oxygen that is combined with haemoglobin in $100\,\text{cm}^3$ blood.
Suggest how oxygen that is not combined with haemoglobin is transported in the blood.
Explain why a long-term smoker would have a lower volume of oxygen combined with haemoglobin in the alveoli at $13.3\,\text{kPa}$.
Describe the function of carbonic anhydrase in the transport of carbon dioxide.
The investigation was carried out again in the presence of carbon dioxide. The volumes of oxygen combined with haemoglobin at partial pressures of oxygen below $8.0\,\text{kPa}$ were lower than those shown in Fig. 5.1. Name this effect and explain the advantage of this decrease at partial pressures of oxygen below $8.0\,\text{kPa}$.