What is the pI of phenylalanine (pK_a1 = 1.8; pK_a2= 9.1)?

Question

Quizplus · Accepted Answer

The pI of an amino acid is the pH at which it has a net charge of zero. To calculate the pI, we need to take the average of the pKa values of the two ionizable groups. For phenylalanine, the two groups are the carboxyl group (-COOH) and the amino group (-NH2). The pKa values are 1.8 and 9.1, respectively. Taking the average of these gives us (1.8 + 9.1)/2 = 5.5, which is the pI of phenylalanine. Therefore, C is the correct answer.

What Is the PI of Phenylalanine (PKa1 = 1

What Is the PI of Phenylalanine (PK_a1 = 1