ATENÇÃO: NÃO É PARA DISCUTIR E SIM PARA TRADUZIR. MENCIONE O PEDAÇO (OU OS PEDAÇOS) QUE VOCÊ TRADUZIU E PUBLIQUE A TRADUÇÃO NO CAMPO DE COMENTÁRIOS.
FP — Let's go back to the life sciences. The first question in your first paragraph is "What are the defining characteristics of living systems?" What is the short answer to that?
FC — Well, the one-word answer is metabolism. Let me take you through a little exercise. If you go around the life science departments and ask, “What is the essential characteristic of life?”,--most people will point out to you that the things that are alive are made of cells, and inside the cells we find macromolecules, long strings of atoms — the proteins, enzymes, lipids, the DNA and so on. To make it even simpler, you can focus on DNA, and you can say, "All you have to do is look for DNA. If there is DNA, it's alive; if there is no DNA, it's not alive." The problem with this definition of life is that, when an organism dies the DNA does not disappear. The DNA is a molecule, which itself is not alive. So, in this wooden chair, for instance, most of the DNA of the wood is still there. My favorite example is that of a team of German scientist who studied the DNA of a Neanderthal skull. These were bones that had been dead for a hundred thousand years or more, and yet the scientists were able to map the sequence of genes in its DNA. So, DNA is not the answer. At the very least, you would have to say we need something that contains DNA and which is not dead. But that, of course is a tautology, to define a living organism as something that is not dead.
So, the answer lies not in the structure of the cell, the answer lies in what philosophers and poets have always called the breath of life. When something has the breath of life, it is alive. In scientific terms, that's what we call metabolism.
Metabolism is the ceaseless flow of energy through a network of biochemical processes, which allows the organism to maintain itself, to repair itself and to perpetuate itself. This metabolism is the essential characteristic of life. Then, if you ask what metabolism is in detail, you have to go into the details of biochemistry and cellular biology.