Proteins are complex formations of amino acids. There are twenty amino acids that occur in proteins and are generally made up of the elements carbon, hydrogen, oxygen and nitrogen. These twenty amino acids can blend in a multitude of different ways to form many different proteins. The amino acids are made up by an amine group (-NH2) and a carboxyl group (-COOH).These long strings of amino acids are held together by peptide bonds to form polypeptides.
Proteins have four levels of structure: primary, secondary, tertiary and quaternary structure. The primary structure of protein is the amino acids (which are linked together by peptide bonds) joining together to form a long string which is called a polypeptide. The peptide bonds that join the amino acids together are a bond that forms between the amine group
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These folds are alpha-helices (spiral shaped) and beta-pleated sheets (flat sheets). Hydrogen bonds hold the structure together by forming between the oxygen and hydrogen atoms on the polypeptide chain and this gives rise to the different shapes formed.
The secondary structure fold together to form the three dimensional tertiary structure. It is held together by varying of bonding. These bonds vary between intermolecular and intramolecular, such as ionic interactions, disulphide bonds, hydrogen bonds and van der waals forces. The tertiary structure is very important to the protein as a whole as this decides the exact shape of the molecule. Proteins can form a variety of different shapes and is key to their roles.
After the tertiary structure has formed they then form a complex structure by joining with different polypeptides or other non-protein prosthetic groups that are important to the function of the protein, this structure is known as the quaternary structure. The bonds holding the quaternary structure together are the same as the tertiary