Final answer:
Decreasing blood pH leads to a reduced affinity of hemoglobin for oxygen due to the Bohr effect, which results in hemoglobin releasing oxygen more readily. Diseases like sickle cell anemia and thalassemia also affect oxygen delivery but through different mechanisms not related to pH changes.
Step-by-step explanation:
Decreasing pH in the blood affects hemoglobin binding by reducing the affinity of hemoglobin for oxygen. This phenomenon is known as the Bohr effect. When blood becomes more acidic due to increased levels of carbon dioxide, this leads to a rise in hydrogen ion concentration, which then causes a decrease in pH. As a result, the oxygen dissociation curve shifts to the right, indicating that oxygen is released more readily from hemoglobin. In other words, as the pH drops, hemoglobin's ability to hold onto oxygen decreases, and more oxygen is required to achieve the same level of saturation as with a higher pH.
Diseases such as sickle cell anemia and thalassemia can also impact the oxygen-carrying capacity of the blood, but their effects are due to changes in hemoglobin structure or red blood cell count, rather than alterations in blood pH. In these conditions, the red blood cells can either be misshapen, as in sickle cell anemia, or contain lower levels of hemoglobin, as in thalassemia, both of which decrease the efficiency in oxygen delivery.