A biochemist adds 1.05 g of a crystalline amino acid to water. After the crystal

Question

A biochemist adds 1.05 g of a crystalline amino acid to water. After the crystalline amino acid dissolves, the biochemist checks the pH and sees that it is 5.97. The label on the bottle that contained the amino acid has mostly faded, so the biochemist is not sure which amino acid she is working with, but she was able to read that pK1 = 2.34 and pK2 = 9.60. She adds 0.01 mol of NaOH, which brings the final volume to 50. mL. She also checks the final pH of the solution and sees that it is 10.0. What is the likely identity of the amino acid? (Use the following atomic weights: 1 for H, 12 for C, 14 for N, 16 for O, and 32 for S.) Report your answer by using the one-letter code.

Explanation / Answer

The isoelectronic point of the given amino acid is 5.97 which matches with the glycine amino acid.

The pKa of NH4+ and COOH also matches with glycine, thus,

Identity of amino acid = Glycine

One letter identity of amino acid = G

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