In some proteins several polypeptide chains fit together to form a larger molecule. The quaternary structure refers to the way the different polypeptide chains fit together.
The final 3D structure of a protein. This structure is produced when the secondary structure of the polypeptide chain is folded.
A covalent S-S bond that joins two cysteine amino acids together, also called an SS-bond or disulfide bond.
Proteins have a primary, secondary, tertiary and sometimes a quaternary structure, and each aspect of the structure is important for the protein to carry out its functions. The bonds which hold amino acids together are peptide bonds. However the complex three dimensional shapes of proteins which enable them to carry out their functions in the cells and the body are created and held together by hydrogen bonds, ionic bonds and disulfide bonds.
The primary, secondary tertiary and quaternary structure of proteins
Hydrogen bonds and sulfur bridges create the complex 3-D shapes of proteins
The structure and functions of proteins are affected by both temperature and pH. Understanding the structure of proteins enables you to understand how temperature and pH have their effect.