What happens to the affinity of hemoglobin for oxygen when it is exposed to increased levels of carbon dioxide?

When hemoglobin is exposed to increased levels of carbon dioxide (CO2), its affinity for oxygen decreases. This phenomenon is part of the Bohr effect, which describes how the binding of CO2 and protons (H+) to hemoglobin alters its structure and function.

The presence of CO2, along with the lower pH that it induces (due to the formation of carbonic acid when CO2 dissolves in blood), promotes the release of oxygen from hemoglobin. This is advantageous in tissues where metabolism is high and CO2 levels rise, allowing hemoglobin to release oxygen more readily where it is needed most.

The decreased affinity for oxygen under these conditions ensures that oxygen delivery to the tissues is optimized, as hemoglobin will bind less tightly to oxygen in environments with higher concentrations of CO2. This physiological mechanism is crucial for effective respiration and metabolism in the body.