Lysine Contains Two Amine Groups (PK_a Values of 9

question 12

Multiple Choice

Lysine contains two amine groups (pK_a values of 9.0 and 10.0) and a carboxylic acid group (pK_a 2.2) . In a solution of pH 9.5, which of the following would best describe the protonation and charge state of lysine?

• A)carboxylic acid: deprotonated and neutral; both amines: protonated and positive
• B)carboxylic acid: deprotonated and negative; both amines: deprotonated and neutral
• C)carboxylic acid: deprotonated and negative; amine (pK_a 9.0): deprotonated and neutral; amine (pK_a 10.0): protonated and positive
• D)carboxylic acid: deprotonated and negative; amine (pK_a 9.0): protonated and positive; amine (pK_a 10.0): deprotonated and neutral
• E)carboxylic acid: deprotonated and neutral; amine (pK_a 9.0): deprotonated and neutral; amine (pK_a 10.0): protonated and positive