general structure of an amino acid, the building blocks of proteins. Each amino acid has a central carbon atom (called the α-carbon) bonded to four different groups: 1. Amino group (-NH₃⁺) → Shown on the left. Contains nitrogen and hydrogens. Acts as a base (can accept a proton). 2. Carboxyl group (-COO⁻) → Shown on the right. Contains carbon double-bonded to oxygen and bonded to a negatively charged oxygen. Acts as an acid (can donate a proton). 3. Hydrogen atom (H) → Shown on top, attached to