Which effect describes the decreased affinity of hemoglobin for O2 as pH decreases?

The correct choice is related to the Bohr effect, which describes the physiological phenomenon where a decrease in pH, indicating increased acidity, leads to a decreased affinity of hemoglobin for oxygen (O2). This effect is crucial for understanding how oxygen delivery is regulated in the body based on the metabolic activity of tissues.

When tissues are metabolically active, they produce carbon dioxide (CO2) and lactic acid as by-products, which lead to an increase in hydrogen ion concentration (lowering pH). As pH decreases, hemoglobin undergoes conformational changes that enhance its release of oxygen. This mechanism is particularly beneficial during periods of high activity when tissues are in need of more oxygen for cellular respiration.

The Bohr effect helps explain why, during exercise or in areas with high carbon dioxide output, the oxygen-hemoglobin dissociation curve shifts to the right. This shift facilitates greater oxygen delivery to tissues that are in greater need, effectively matching oxygen supply with demand.

In contrast, the Henderson effect refers to the interaction of CO2 with water to form carbonic acid and its subsequent dissociation, influencing acid-base balance but not directly relating to hemoglobin's oxygen binding. The chloride shift involves the exchange of bicarbonate and chloride ions across cell