Haemoglobin's oxygen binding affinity is inversely related to which factors?

Haemoglobin's oxygen binding affinity is inversely related to both acidity (pH) and carbon dioxide concentration due to the Bohr effect. When carbon dioxide levels increase in tissues during metabolic activity, it leads to a decrease in pH (increased acidity) because carbon dioxide reacts with water to form carbonic acid.

This decrease in pH, along with the increase in carbon dioxide levels, stabilizes the deoxygenated form of haemoglobin, which lowers its affinity for oxygen. As a result, haemoglobin releases more oxygen to the tissues that need it. This mechanism is crucial for efficiently delivering oxygen where it is most utilized in the body, especially during times of increased metabolic demand, such as exercise.

The other factors listed do not have the same direct relationship with haemoglobin's oxygen affinity. While temperature can affect oxygen binding, it is not as strong of a direct inverse relationship as with acidity and carbon dioxide. Osmotic pressure, blood pressure, and blood volume do not directly affect haemoglobin’s affinity for oxygen in the same way that changes in pH and carbon dioxide concentrations do. Thus, the connection between acidity, carbon dioxide levels, and haemoglobin's oxygen binding affinity is a fundamental aspect of respiratory physiology.