Final answer:
The amino acid isoleucine contains a central alpha carbon bonded to an amino group, a carboxyl group, a hydrogen atom, and a hydrophobic butyl side chain with a branch.
Step-by-step explanation:
The structure of the amino acid isoleucine involves a central alpha carbon (a-carbon), which is attached to four distinct groups: an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen atom (H), and a unique side chain or R group that defines the amino acid. Isoleucine's R group is a hydrocarbon chain with a branch, specifically a butyl group with a one-carbon branch on the second carbon, which makes this amino acid nonpolar and hydrophobic. This specific structure contributes to the protein folding process, as it will generally be found in the interior of protein structures, away from water.