What are the three protein structures?

Primary structure. There are 20 different standard L-α-amino acids used by cells for protein construction. Amino acids, as indicated by their name, contain both a basic amino group and an acidic carboxyl group. This difunctionality allows individual amino acids to combine into long chains through the formation of peptide bonds.

Secondary structure. Stretch marks or strands of proteins or peptides have distinct characteristic local structural conformations or a secondary structure dependent on hydrogen bonding. The two main types of secondary structure are the α-helix and the β-helix.

Tertiary structure. The overall three-dimensional shape of the entire protein molecule is a tertiary structure. The protein molecule will bend and twist in such a way as to achieve maximum stability or lowest energy state. Although the three-dimensional shape of a protein may seem irregular and random, it is formed by many stabilizing forces due to the binding interactions between groups of the amino acid chain.