A Level Biology Practice Exam

What term describes the change in hemoglobin's affinity for oxygen due to the presence of carbon dioxide?

1. Haldane effect

2. Bohr effect

3. Fick's principle

4. Oxygen dissociation curve

The correct answer is: Bohr effect

The correct answer is the Bohr effect, which refers to the physiological phenomenon where an increase in carbon dioxide concentration leads to a decrease in hemoglobin's affinity for oxygen. This occurs because carbon dioxide and protons (H⁺ ions) influence the molecular structure of hemoglobin, causing it to release oxygen more readily. This mechanism is crucial for efficient oxygen delivery in tissues that are metabolically active, as they tend to produce more carbon dioxide. The Haldane effect is related but specifically describes how deoxygenated hemoglobin can carry more carbon dioxide than oxygenated hemoglobin. Fick's principle pertains to the relationship between diffusion and the movement of gases and does not directly relate to hemoglobin's affinity for oxygen. The oxygen dissociation curve depicts the relationship between oxygen saturation of hemoglobin and the partial pressure of oxygen, showcasing how various factors—including pH and carbon dioxide levels—affect this saturation, but it doesn't define a specific term related to the change in affinity itself.