The Bohr effect is due in part to
A) relatively low pKa (i.e. weaker base) for histidyl residues because of their proximity to ionized aspartyl residues in oxyhemoglobin.
B) a relatively high pKa (i.e. stronger base) for histidyl residues because of their proximity to arginyl residues in deoxyhemoglobin.
C) a relatively high pKa for histidyl residues because of their proximity to ionized aspartyl residues in deoxyhemoglobin.
D) a relatively low pKa for histidyl residues because of their proximity to arginyl residues in deoxyhemoglobin.

Question

Quizplus · Accepted Answer

The Bohr effect describes the phenomenon in which hemoglobin releases more oxygen in tissues with a lower pH (i.e. more acidic conditions). This is due to the fact that in acidic conditions, histidine residues in hemoglobin have a higher pKa, making them more likely to become protonated and thus releasing oxygen more readily. This is specifically due to the proximity of these histidine residues to ionized aspartate residues in the deoxygenated (and more acidic) state of hemoglobin. Therefore, choice C, which describes a relatively high pKa for histidyl residues because of their proximity to ionized aspartyl residues in deoxyhemoglobin, is the best choice.

The Bohr Effect Is Due in Part to