Chapter 21, Problem 51P

A titration curve is a plot of the pH of a solution as a function of added equivalents of hydroxide ion. As hydroxide ion is added to the aqueous solution, the pH increases because hydroxide ion removes protons from the solution. The pH flattens out when hydroxide ion can remove a proton from an ionziable group of an amino acid rather than a proton from the solution. Identify the amino acids that give the titration curves below.