Which of the following factors does not affect the oxygen dissociation curve?
Carbon dioxide concentration
pH level
Temperature
Red blood cell count
The factors that affect the oxygen dissociation curve include carbon dioxide concentration (Bohr effect), pH level (Bohr effect), and temperature. Changes in these factors can cause shifts in the curve, influencing the affinity of hemoglobin for oxygen and its release to the tissues. However, the red blood cell count does not directly affect the oxygen dissociation curve. Red blood cell count refers to the number of red blood cells in the blood and does not have a direct impact on the binding and release of oxygen by hemoglobin. Hence, option 4 is the correct answer.