Shown is the amino acid tryptophan. Put the letter “C” at the site of every carbon atom. Label the amino group, the carboxyl group, and the side group.

Verified step by step guidance

1. Identify the structure of tryptophan, which is an amino acid composed of a central alpha carbon bonded to an amino group, a carboxyl group, a hydrogen atom, and a distinctive side chain (indole group).
2. Locate every carbon atom in the molecule. This includes the alpha carbon (central carbon), the carbons in the carboxyl group (COOH), the carbons in the side chain (the indole ring system), and any other carbon atoms present.
3. Mark each carbon atom by placing the letter "C" at its position on the structure. Remember that the carboxyl group contains one carbon atom, and the side chain of tryptophan contains multiple carbons arranged in a bicyclic indole ring.
4. Label the amino group by identifying the nitrogen atom bonded to two hydrogens (–NH2) attached to the alpha carbon. Write "Amino group" next to it.
5. Label the carboxyl group by identifying the carbon double bonded to an oxygen and single bonded to a hydroxyl group (–COOH) attached to the alpha carbon. Write "Carboxyl group" next to it. Then, label the side group (the indole ring) attached to the alpha carbon as "Side group".

Key Concepts

Structure of Amino Acids

Amino acids have a central carbon atom (alpha carbon) bonded to an amino group, a carboxyl group, a hydrogen atom, and a unique side chain. Understanding this basic structure helps identify the location of carbon atoms and functional groups in any amino acid.

Functional Groups in Amino Acids

The amino group (-NH2) and carboxyl group (-COOH) are key functional groups in amino acids. The amino group acts as a base, and the carboxyl group acts as an acid, both playing crucial roles in peptide bond formation and protein structure.

Side Chain (R Group) of Tryptophan

Tryptophan’s side chain is a complex indole ring containing carbon and nitrogen atoms. Recognizing the side chain structure is essential for labeling it correctly and distinguishing it from the amino and carboxyl groups.