Western Governors University (WGU) CHEM3501 C624 Biochemistry Objective Assessment Practice Exam

Hemoglobin's affinity for oxygen is indeed influenced by pH, a phenomenon known as the Bohr effect. An increase in pH (meaning a shift toward a more alkaline environment) results in hemoglobin having a higher affinity for oxygen. This happens because higher pH levels reduce the concentration of protons (H+ ions) in the blood, which leads to changes in the conformational state of hemoglobin.

When the pH is higher, there is less protonation of histidine residues on the hemoglobin molecule, which stabilizes the R state (relaxed state) of hemoglobin that binds oxygen more tightly. Therefore, at constant partial pressures of oxygen, an increase in pH elevates hemoglobin's ability to bind oxygen, leading to greater oxygen saturation.

In contrast, a lower pH increases the concentration of hydrogen ions, which promotes the T state (tense state) of hemoglobin, thus decreasing its affinity for oxygen. Understanding the relationship between pH and hemoglobin's affinity for oxygen is crucial in contexts such as respiratory physiology, where pH can fluctuate based on metabolic activity.