Living Cells, Lifeless Molecules

Cells are composed of molecules that are lifeless but special, because most of them occur in nature only in the context of life. They are essential to all the workings of life, and no one single class holds life’s secret: life is an emergent property of the collective of molecules, assembled into the elaborate structures called cells. Cells come in great profusion, but all are variations on just two patterns of organization: prokaryotes, small and relatively simple microbes, both Bacteria and Archaea; and eukaryotes (Eukarya), the larger and more complex cells that make up all animals, plants, and fungi. The molecules of life, for all their diversity, again fall mainly into just a handful of categories. The bulk of living matter consists of proteins, nucleic acids, carbohydrates and lipids. Biomolecules belong to chemistry, but their functions in the process of living place them in the realm of biology.