Which of the following amino acids has its isoelectric point at the highest pH?

Question

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Lysine is a basic amino acid with a positively charged amino group (NH3+) at physiological pH (7.4). As pH increases, the amino group will progressively become deprotonated, resulting in a negative charge. At the isoelectric point, lysine will have equal amounts of positive and negative charges, resulting in a net charge of 0. The isoelectric point of lysine is around pH 10.8, which is the highest pH among the given amino acids.

Which of the Following Amino Acids Has Its Isoelectric Point