Protein function

Protein folding is essential to the overall function of the individual protein. Polypeptide chains are often very long and flexible, which leads to a wide variety of ways for a protein to fold. Non-covalent interactions control the shape and structure of the nascent protein. While a single non-covalent bond is very weak, a combination of many weak bonds provide the needed strength and structure for a given protein. Electrostatic interactions, hydrophobic interactions, hydrogen bonds and van der Waals attractions all aid in protein folding. The specific polar and non-polar side chains of amino acids are also involved the protein's folding and, in turn, its function.[51] The final folded structure of a protein is protein's conformation.[52] A protein's proper amino acid sequence is absolutely required to induce proper folding into the quaternary structure. Two common folding patterns seen in proteins are the alpha helix and beta sheets.

The function of a protein is directly determined by its structure, specifically the aforementioned non-covalent bonds. Proteins interact with other molecules at unique protein binding sites on the ligand.[53] Proteins can have a myriad of functions, including the enzymatic catalysts which facilitate essential reactions in cells.[54] Proteins can also act as a cell signal receptor, essential to initiating cellular responses to chemical signals, or as motor proteins, which are involved with movement of or within individual cells. Another example of protein function is that of structural proteins, which enable cell flexibility and support stability.[54]