The science that describes the structure, interactions, and reactions of organic compounds of biological significance at the molecular level. It represents the meeting of biochemistry, as attempts are made to describe the structure and physiology of organisms on an ever smaller scale, with organic chemistry, as attempts are made to synthesize and understand the behavior of molecules of ever-increasing size and complexity. Areas of research include enzymatic catalysis, the structure and folding of proteins, the structure and function of biological membranes, the chemistry of poly(ribonucleic acids) and poly(deoxyribonucleic acids), biosynthetic pathways, immunology, and mechanisms of drug action.