What is the structure of a protein?

Proteins are long chains of amino acids connected by peptide bonds. The structure of proteins is broken down into 4 components. The primary structure of a protein is simply the order of amino acids found in the protein. It could be represented like this: Ser-Val-Lys-Gly-... etc. The secondary structure of a protein describes the 3-dimensional shapes formed by stretches of amino acids within the protein. Most commonly, stretches of amino acids will form either alpha helices or beta sheets (also called beta-pleated sheets). The tertiary structure of a protein describes the 3 dimensional arrangement of the alpha helices and beta sheets. Both secondary and tertiary structure can be held in place by ionic bonds, hydrogen bonds, or disulphide bridges. Some proteins are made up of multiple subunits, and in these proteins, the way the subunits fit together and are arranged in space is the Quaternary structure.