How is the Bohr effect characterized in terms of pH and O2 affinity?

The Bohr effect is characterized by a decrease in pH leading to a decreased affinity of hemoglobin for oxygen. When pH decreases, which often occurs in the presence of increased carbon dioxide (CO2) and lactic acid (like during exercise), the oxygen binding curve of hemoglobin shifts to the right. This means that hemoglobin releases oxygen more readily to the tissues, as the acidic environment promotes the release of oxygen from hemoglobin into the cells that require it for metabolic processes.

In this context, a decrease in pH is closely associated with the physiological conditions that enhance oxygen delivery. Additionally, this effect can be compounded by an increase in 2,3-DPG—a molecule that also shifts the hemoglobin-oxygen dissociation curve to the right, facilitating oxygen release.

Thus, a decreasing pH, along with other factors, leads to a reduction in the affinity of hemoglobin for oxygen, which is a key aspect of the Bohr effect.