Which of the following factors decreases the binding affinity of hemoglobin for oxygen?

The binding affinity of hemoglobin for oxygen can be influenced by several physiological conditions. Increased temperature and higher concentrations of bisphosphoglycerate (BPG) are known to decrease hemoglobin's affinity for oxygen.

When temperature rises, the structure of hemoglobin changes slightly, leading to a reduced ability to bind oxygen. This shift allows hemoglobin to release oxygen more readily to tissues that may be more metabolically active and require more oxygen.

Similarly, BPG binds to hemoglobin and stabilizes the deoxygenated form of the protein. This binding lowers hemoglobin's affinity for oxygen, promoting oxygen release to the tissues. High concentrations of BPG often occur in situations where the body requires more oxygen delivery, like during strenuous exercise or at high altitudes.

In contrast, increased pH levels typically increase the affinity of hemoglobin for oxygen, a phenomenon known as the Bohr effect. This means that the conditions mentioned in the correct choice lower hemoglobin’s binding affinity, facilitating better oxygen delivery under those circumstances. Hence, the combination of increased temperature and higher BPG concentrations effectively reduces hemoglobin's ability to hold onto oxygen.