DESCRIPTION
Proteins are one of the four major types of organic compound and are extremely important for all cells and organisms. Proteins are made up of one or more polypeptide chains and the subunits of polypeptide chains are called amino acids. Proteins perform many different functions in living things and their 3D structure is critical to their function. The structure of a protein is determined by the specific sequence of amino acids in the polypeptide chain/s. Biologists describe the structure of proteins at four levels - primary, secondary, tertiary and quaternary structure.
