Final answer:
Amino acids are the building blocks of proteins and have a common structure consisting of a central carbon atom, an amino group, a carboxyl group, a hydrogen atom, and an R group. The R group is the only variable part of the amino acid and determines its properties.
Step-by-step explanation:
Amino acids are the building blocks of proteins, and each amino acid has the same basic structure. It consists of a central carbon atom bonded to an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom, and an R group. The R group is the only variable part of the amino acid, and it determines the unique properties of each amino acid.