This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: JIPMER 2018, Subject name: Biochemistry
Which of the following is the most effective buffer for pH of 7.4? 
Select and explain. 
A. Carbonic acid buffer with pKA-6.1, B. Phosphate buffer with pKA of 6.9, C. Glutamate buffer with pKA-8.7, D. Acetate buffer with pKa 4.5
B: Phosphate buffer with pKA of 6.9
Answer: B: Phosphate buffer with pKA of 6.9 
Explanation: Blood pH - 7.4 Buffer is most effective when pH = pKA +- 1 Therefore the most effective buffer for pH- 7.4 will be the one whose pKA +- 1 will cover this pH. Out of given options pKA +- 1 of phosphate buffer (5.9 to 7.9) covers pH 7.4. So most effective buffer for blood will be Phosphate buffer with pKA of 6.9.