According to the Bohr effect, how does decreasing pH (more acidic conditions) affect the oxygen affinity of hemoglobin?

Introduction:
The Bohr effect describes how hemoglobin's oxygen-binding affinity is modulated by pH and carbon dioxide. Physiologically, tissues produce acid and CO2 during metabolism, signaling hemoglobin to release oxygen where it is needed. This question checks your understanding of the direction of the affinity change when pH falls.

Given Data / Assumptions:

• Lower pH corresponds to more protons in solution.
• CO2 hydration in blood generates carbonic acid, lowering pH.
• Hemoglobin exhibits cooperative oxygen binding regulated by allosteric effectors.

Concept / Approach:
Protonation of specific hemoglobin residues stabilizes the T (tense) state relative to the R (relaxed) state. Stabilizing T reduces oxygen affinity, shifting the oxygen dissociation curve to the right, thereby facilitating oxygen release in acidic, metabolically active tissues.

Step-by-Step Solution:

Verification / Alternative check:
Clinical and physiological data show that acidosis (lower pH) reduces saturation at a given partial pressure of oxygen, consistent with the Bohr effect; alkalosis produces the opposite.

Why Other Options Are Wrong:

• Increase affinity or no effect: contradicts the Bohr effect.
• Tissue-specific increases: the effect is systemic and context-driven by pH and CO2, not an exception limited to muscles or lungs.

Common Pitfalls:
Confusing Bohr effect (pH and CO2 influence) with the Haldane effect (oxygenation of blood affecting CO2 transport).

Final Answer:
decrease in oxygen affinity