Hemoglobin’s affinity for oxygen decreases when:
A the pCO2 in the body decreases.
B body temperature decreases.
C body temperature increases.
D blood pH increases.
The correct answer and explanation is:
The correct answer is C. body temperature increases.
Hemoglobin’s affinity for oxygen is influenced by several factors, and one of the most important is temperature. When the body temperature increases, hemoglobin’s affinity for oxygen decreases. This means hemoglobin is more likely to release oxygen to tissues that need it.
The relationship between temperature and oxygen affinity is explained by the Bohr effect. When tissues are active and produce more heat due to metabolism, the increased temperature causes a decrease in hemoglobin’s affinity for oxygen. This allows more oxygen to be released from hemoglobin and delivered to the tissues that require it. This is particularly important during exercise or in areas of inflammation where the tissues require more oxygen.
In contrast, if the body temperature decreases, hemoglobin’s affinity for oxygen increases. This helps to conserve oxygen in the body by binding more tightly to it, which is useful in colder conditions where oxygen demand is lower.
The other options are incorrect for the following reasons:
- A. the pCO2 in the body decreases: A decrease in carbon dioxide (CO2) levels would increase hemoglobin’s affinity for oxygen, making it less likely to release oxygen to tissues.
- B. body temperature decreases: As noted, lower temperatures increase hemoglobin’s affinity for oxygen, so this would make hemoglobin hold onto oxygen more tightly.
- D. blood pH increases: An increase in pH (alkalosis) also increases hemoglobin’s affinity for oxygen, making it less likely to release oxygen to tissues.
In summary, when the body temperature increases, hemoglobin releases oxygen more readily to the tissues, which is essential during high metabolic demand situations like exercise or fever.