Question detail

Which groups are present in an amino acid that contribute to zwitterion formation?

Try the question, check the answer, then read the explanation to understand the curriculum point.

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At a glance

MCQ

Type

practice

Style

Topic

Amino acids, proteins and DNA (A-level only)

Question

A. Amine and hydroxyl groups
B. Carboxylic acid and hydroxyl groups
C. Amine and carboxylic acid groups
D. Carboxylic acid and aldehyde groups

Answer

Amine and carboxylic acid groups

Explanation

Amino acids contain both amine (-NH2) and carboxylic acid (-COOH) groups, which allow them to exist as zwitterions when the carboxylic acid donates a proton to the amine, resulting in a positive and negative charge within the same molecule.

Common mistake

Zwitterion misconception

Students think a zwitterion is a neutral molecule with no internal charges.

Explain that a zwitterion contains both a positively charged ammonium group (–NH₃⁺) and a negatively charged carboxylate group (–COO⁻) on the same amino‑acid, giving a net zero charge but internal charges that must be considered when describing its formation.

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