Identifying Amino Acids with Sulfur

Amino acids are the building blocks of proteins and play crucial roles in various biological processes. Each amino acid has a characteristic side chain that determines its properties and functions. Among the 20 standard amino acids, some are classified as nonpolar, polar, or charged. Understanding the classification and properties of these amino acids is essential for grasping how proteins fold and function.

Which of the following amino acids contains a sulfur atom in its side chain?