- Articulation of the text
Defining life requires the establishment of the general characteristics of all living beings, and showing how living matter differs from inanimate matter. Until the nineteenth century, many writers and theorists of vitalism, believed that living things had characters so different from those of inanimate matter, that their existence depended probably on a "vital force" of presumed unknown physics. Today, there is no doubt that this distinction is justified. The basic unit of all living things is the cell. This is necessarily bounded by a membrane and is capable of replication. It is the seat of metabolism of biochemical reactions which are, firstly, a degradation of substances and, secondly, summaries (usually molecules giants such as proteins or nucleic acids). Degradation reactions provide the materials and energy needed for synthesis reactions, which can build or restore cell components such as enzymes (proteins that carry out each step of metabolism) membranes and genetic material.