What describes the Bohr effect?

What describes the Bohr effect?

• A. Increased CO2 promotes O2 release.
• B. Increased O2 promotes CO2 release.
• C. Increased CO2 promotes O2 binding.
• D. Increased pH promotes O2 release.

Answer: (A)

The Bohr effect describes how increases in CO2 (and the accompanying rise in hydrogen ions that lowers pH) reduce hemoglobin’s affinity for oxygen, promoting oxygen release where it’s most needed. In tissues, metabolism produces CO2, which diffuses into red blood cells and, via carbonic anhydrase, forms carbonic acid that dissociates into H+ and bicarbonate. The rise in H+ lowers pH, stabilizing the deoxygenated form of hemoglobin and decreasing its grip on O2, so more O2 is released to the tissues. In the lungs, CO2 is expelled, pH rises, and hemoglobin’s affinity for O2 increases, facilitating oxygen binding. Therefore, increased CO2 promotes O2 release, which is exactly the effect described. The other ideas don’t fit because higher CO2 would not enhance O2 binding, and higher pH would actually favor tighter O2 binding rather than release.

The Bohr effect describes how increases in CO2 (and the accompanying rise in hydrogen ions that lowers pH) reduce hemoglobin’s affinity for oxygen, promoting oxygen release where it’s most needed. In tissues, metabolism produces CO2, which diffuses into red blood cells and, via carbonic anhydrase, forms carbonic acid that dissociates into H+ and bicarbonate. The rise in H+ lowers pH, stabilizing the deoxygenated form of hemoglobin and decreasing its grip on O2, so more O2 is released to the tissues. In the lungs, CO2 is expelled, pH rises, and hemoglobin’s affinity for O2 increases, facilitating oxygen binding. Therefore, increased CO2 promotes O2 release, which is exactly the effect described. The other ideas don’t fit because higher CO2 would not enhance O2 binding, and higher pH would actually favor tighter O2 binding rather than release.