Amino acids incorporated into protein structures are of the L form . Amino acids link together between the amide and carboxyl groups. Two amino acids bind together and eliminate water resulting in a peptide link. What is left is referred to as an amino acid residue. If this chain becomes very long, it is then called a polypeptide.
All proteins are polypeptides of a defined sequence of amino acids.
Structures a Protein can Take There are four different structures a protein can have. The first structure is primary structure. This is just a chain of amino acids linked together. Secondary structure results from hydrogen binding between the amide and the carboxyl of groups that are not very far apart on the backbone of the protein. This can make structures such as alpha helicies, beta sheets, and beta turns.