Which two functional groups are always found in amino acids?

• A. Carbonyl and amino groups.
• B. Carboxyl and amino groups.
• C. Amino and sulfhydryl groups.
• D. Hydroxyl and carboxyl groups.

Answer: (B)

Verified step by step guidance

1. Understand the basic structure of an amino acid, which consists of a central carbon atom (alpha carbon) bonded to four different groups: an amino group, a carboxyl group, a hydrogen atom, and a variable R group (side chain).
2. Identify the amino group, which is a functional group consisting of a nitrogen atom bonded to two hydrogen atoms, represented as \($\mathrm{NH}$₂\). This group is always present in amino acids.
3. Recognize the carboxyl group, which is a functional group consisting of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group, represented as \($\mathrm{COOH}$\). This group is also always present in amino acids.
4. Compare the given options with the known structure of amino acids: Carbonyl and amino groups, Carboxyl and amino groups, Amino and sulfhydryl groups, Hydroxyl and carboxyl groups.
5. Determine that the correct answer is 'Carboxyl and amino groups' because these are the two functional groups that are consistently found in all amino acids.