An amino acid is an organic molecule that contains both an amine group and a carboxyl group. At neutral pH, which structure is most likely:

Question

Quizplus · Accepted Answer

At neutral pH, the amine group will act as a base and accept a proton (H+), becoming positively charged (+NH3). Similarly, the carboxyl group will act as an acid and donate a proton (H+), becoming negatively charged (-COO-). Therefore, the most likely structure at neutral pH is a zwitterion, where the amine and carboxyl groups are ionized and the molecule overall has no net charge. This is represented by structure (b), where the amine group has a protonated nitrogen atom and the carboxyl group has a deprotonated oxygen atom. Structure (a) represents an amino acid at a low pH, where the carboxyl group is fully protonated and the amine group is neutral.

An Amino Acid Is an Organic Molecule That Contains Both