JEE Main levelSingle correct optionDifficulty 2 of 3bm256
The amino acid shown has pKa1=2.34 and pKa2=9.60. What is its isoelectric point?
A7.47
B5.97
C11.94
D3.57
Answer: B
For an amino acid with no ionisable side chain, pI=(pKa1+pKa2)/2=(2.34+9.60)/2=5.97. The compound is glycine; the other values come from subtracting or adding the pKa values or averaging wrongly.