This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Gas Transport, Subject name: Physiology
All of the following factors influence hemoglobin dissociation curve, except: 
Select and explain. 
A. Chloride ion concentration, B. CO2 tension, C. Temperature, D. 2-3 DPG levels
A: Chloride ion concentration
Answer: A: Chloride ion concentration 
Explanation: Ans. is 'a' i.e. Chloride ion concentration Three conditions affect the oxygen-hemoglobin dissociation curve, the pH, the temperature, and the concentration of 2, 3-biophosphoglycerate.CO2 tension (PCO2) affects the pH of blood and hence the 02-Hb dissociation curve.Shift of Q2-Hb dissociation curveFactorsShift to RightShift to leftpH||temperature||2, 3 DPG cone.||PCO2||