Final answer:
Amino acids join together in chains through peptide bonds to form proteins, with the sequence of these acids determining the protein's structure and function.
Step-by-step explanation:
When amino acids join together in chains, they create proteins. This linkage is made through a peptide bond between the carboxyl group of one amino acid and the amine group of another, releasing a molecule of water in a process known as a condensation reaction. As more amino acids join, this forms a polypeptide chain which can fold and function as a protein. The sequence of amino acids in a protein determines its unique structure and function.