For the Peptide Ala-His-Glu-Val-Asp-Cys-Lys-Leu, What is the Net Charge at PH

Question

For the peptide Ala-His-Glu-Val-Asp-Cys-Lys-Leu, what is the net charge at pH 3?
A) -1
B) 0
C) +1
D) +2
E) +3

Accepted Answer

At pH 3, the N-terminus (Ala) is protonated (+1), the C-terminus (Leu) is not ionized (0), His is protonated (+1), Glu and Asp are not ionized (0), Cys is not ionized (0), and Lys is protonated (+1). The net charge is +3.