Final answer:
When lung pH is at 7.4, hemoglobin has a stable affinity for oxygen, which allows it to pick up oxygen effectively. A more acidic blood pH, caused by higher CO2 levels, reduces hemoglobin's affinity for oxygen, but at pH 7.4 the oxygen dissociation curve is in optimal position for oxygen transport.
Step-by-step explanation:
At a lung pH of 7.4, hemoglobin in red blood cells can optimally pick up oxygen. This pH level is crucial for maintaining the balance between the affinity of hemoglobin for oxygen and its release in body tissues. If the blood becomes more acidic (lower pH), the affinity of hemoglobin for oxygen is reduced; this phenomenon is described by the Bohr effect. In other words, a decrease in pH, which occurs with increased levels of carbon dioxide (CO2) in the blood, would result in the release of oxygen from the hemoglobin. However, at pH 7.4, the affinity of hemoglobin for oxygen remains stable, promoting the uptake of oxygen to form oxyhemoglobin, which is necessary for efficient oxygen transport to body tissues where it will dissociate based on the local demand for oxygen.