What is life?

In the first two lectures, we will deal with chemistry rather than theology. I consider it necessary and important. If we are to think about our lives’ meaning, it is useful to try to answer what it is, first actually, life. We will see that the answer is not so simple. Man is alive; a piece of concrete is not alive. The difference is clear because even a small child can distinguish living beings from inanimate things. Except when deeper, let’s think about the question, the differences between the living and the non-living will quickly blur us. Biologists are thinking about defining life several characteristics of life but recall that none of them can be considered separately from others. These are metabolism, heredity, hierarchical arrangement, and composition of so-called nuclear acids and proteins.

Metabolism is the conversion of substances and energies. We all know us alive systems take in some substances from their surroundings and get rid of some substances. We breathe oxygen and get rid of carbon dioxide. We eat and excrete. All living organisms do so do. A chemist would say that a living organism is a thermodynamically open system.
Another unique property of living organisms is reproduction. Life can make its copy.  So far, not even the most perfect computer can do this. Some machines can create other complex machines, but so far, no human invention can copy itself. Only a living creature can do this. Reproduction introduces us.

In the strict sense of the word, it is not a copy. If we omit the environment’s impact, it’s about copies that can speak only in the case of asexually reproducing their organisms. In sexual creatures, it would be better to speak of “individuals like themselves.” The child is neither a copy nor an average of the parents and their characteristics. Maybe it looks a bit like walking in a circle,  but mortality, though we cannot use it to define life, points to the need for heredity. So far, we do not know any organism that would live forever. For that, Inheritance is necessary – it’s about being able to move on give up your qualities.

Inheritance is what is considered in evolution. Imagine the perfect animal perfectly adapted to the environment in which it lives, with sharp teeth, penetrating eyes, and fast legs; it did not know how to pass on his qualities to his descendants, all his benefits they would perish along with his death and would be lost forever. Another important feature of living systems is their cellular organization. All living organisms known to us are made up of cells. After years spent in school desks, it no longer seems strange – but why, for example, would an elephant have to consist of many, many small chambers? We can generalize the whole principle and say that the living system is its own hierarchical organization.

We can imagine the hierarchy of all nature as follows: the strings are
they fold into quarks. Quarks are composed of elementary particles.
Elementary particles are composed of atoms. The atoms are composed of molecules. Amino acid molecules are made up of protein chains; nucleotide molecules are folded into nucleic acid strands, monosaccharide molecules are folded into starch, chitin, or cellulose chains; these long molecules, consisting of many small, we call polymers. The polymers are folded into so-called organelles in the cell. The organelle in the cell is a state in the state, a department with a certain autonomy level. Organelles are assembled into cells. The cells are they fold into tissues, such as muscle tissue. The tissues of the glass are placed in the organs. An example is a heart. The bodies are composed of organ systems, for example, the circulatory system, i.e., the heart, blood, and blood vessels. Different organ systems make up an individual. Individuals, deer or wolves, make up the population. Groups of different species of animals and plants together with rocks and minerals then form an ecosystem. Ecosystems form a planet.

Mortality is not a quality by which we can define life. What is alive is mortal. What is mortal is alive; this tautological definition tells us nothing at all. The last property of life on Earth is its chemical composition. All organisms known to us are composed of nucleic acids and proteins. Surprisingly, we do not know life on this planet that would not use it as a building and regulatory element of protein and as a logistical and a nucleic acid information medium. On other planets, it can; however, the situation may be different. And we would show the complexity of the definition of life; let’s do it a short trip to space. The closest candidate for the existence of life outside the earth is Jupiter’s moon Europe. Although at first glance it resembles our Moon, which has no visible signs of life and is furrowed with craters, Europe is covered in ice. Maybe down somewhere from this freezing shell, gravitational pressures created enough heat for water to exist here in liquid form.

That is already a very hope situation to discover something alive; in any case, the conditions for the life of our type in Europe are much more favorable than those who ruled four billion years ago here on Earth. Now imagine yourself just landing in Europe if an astronaut. You’re in luck, you came across some lucky coincidence down in the crater for running water, and in it, you have discovered a floating object. Is he alive or not? Maybe you would get something into the subject. First, they stabbed, and you would try to provoke a response. If the subject of the couples, it would be interesting. If he stayed calm, you wouldn’t be able to do anything – not even living trees from Earth would not move when touched. Maybe you would like them to try to cut the object to discover a possible cellular structure and try to estimate its chemical composition – here I have the advantages, fortunately: the whole visible universe consists of the same known elements of the Mendeleev system as we know from earthly home,
so some big surprise shouldn’t happen. But if you found that the object could reproduce, that would be very interesting, though not decisive.

Here we end our thought experiment and return home to Earth. Well, even here, our search is not without problems. The wonderful formations dull the exact cut between life and non-life we call viruses. Anyone who has ever had the flu knows what they can do. However, the data from May 2002 brings bad news to all those who support life in Europe: the ice sheet seems much thicker than expected. But we don’t know about viruses, whether they are alive or not. Strictly speaking, they are not; they do not fit into the diffusion requirements, which is the crucial reason: viruses have no metabolism. On its way through the air, the influenza virus, for example, behaves as unequivocally inanimate a thing in a tram. He takes nothing from the environment and returns nothing to it. He can’t reproduce in this state. It doesn’t even have irritability. It’s simply about just a piece of chemical that we can describe thanks to chemical formulas, namely with a more complex structure, such as water or ethanol, but which is more like the simplest cell. And yet, if the virus enters a suitable environment, for example, if the unsuspecting passenger inhales him, he suddenly begins to behave as if he were alive. It can chemically bond to a suitable cell, force its genetic information and, under favorable conditions, either survive or multiply successfully and eventually destroy the cell. So, we’re at the end of our definition. The virus can do such pieces that no other piece of inanimate matter can do but of known ones; For reasons we cannot say he is alive. Like Tolkien’s name, viruses are spheres, neither dead nor alive, moving in the earth one, at the interface between life and non-life.
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