Amino Acids & Protein Structure

Intermolecular Forces

The Cardiovascular System

Multiple-subunit proteins possess a quaternary structure. In other words, quaternary structure describes proteins with more than one peptide chain. Hemoglobin is one such molecule, consisting of four polypeptide chains held together by noncovalent forces (intermolecular forces and salt bridges). Other examples of proteins with quaternary structure include DNA polymerase and many transmembrane channels.