| Sumario: | The interplay of chemistry and biology that occurred after Lavoisier's revolution gave the possibility of analysing the first organic molecules present in animals and plants. The will of learning of the first biologists enabled them to gain the biological meaning of many organic molecules and, towards the mid-19th century, to introduce the concept of "metabolism" for explaining the transformation of food into heat and products for both animal and plant tissues. This concept changed the course of both the experimental biology and medicine and made official, almost in an obvious way, the success of biochemistry as the most appropriate discipline for studying cell metabolism. After the discovery of proteins and nucleic acids as the macromolecules of the genetic code, the words "molecular biology" replaced the word biochemistry but this replacement was nominalistic, because the molecular mechanisms involved in growth and development of the organisms are fundamentally of biochemical nature. In this context, life represents a biochemical phenomenon endowed with a specific internal coherence, resting on two fundamental processes: i) a program, expressed by the genetic code, and ii) a modulation of the complex cell metabolism, with the production of chemical work, heat and homeostasis. This conception of life excludes any external planning design, as well as any deterministic and teleological interpretation, and may be considered of validity for the whole evolutionist span, from the formation of the first protocells to the appearance of man.
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