In this sense, we are talking about metabolism, which is in fact, a slow controlled combustion reaction where there is an ignition – the moment when the living being is born and begins to inhale oxygen which is the oxidizer for all combustion – and a fuel, the food consumed by each living being. Before we talk about this slow combustion that takes place inside each living thing, let us talk about combustion in general.
The Process of Combustion
Combustion is a chemical reaction between two substances: a fuel and an oxidizing agent, that is, something that facilitates or makes the combustion possible. The oxidizer is always oxygen, and all fuels have something in common: they are of organic origin, that is, they were once living organisms with carbon chains linked to hydrogen or oxygen atoms.
If this is the case then how does our star, the sun, carry out combustion where there is no oxygen and no organic matter? Combustion on Earth is a chemical reaction. Inside the sun and all the stars, combustion is a nuclear reaction; in other words, the pressure inside the sun is so immense that energy is released by nuclear fusion of hydrogen nuclei into helium.
Back to our reality on Earth, for a combustion reaction to take place, it is not enough to just have a fuel; we need an oxidizer to help in the process or to make it possible. Take a lighted candle, for example – it can burn for hours until all the wax is burned off; but if we put it under a glass dome, it will continue to burn only until all the oxygen is used up. Without the oxidizer and still with a lot of fuel, the flame will nevertheless go out.
In addition to the fuel and the oxidizer, there is still a third component that is essential for combustion: the ignition. The candle does not come lit, someone has lit it; even in the presence of oxygen, the candle would not burn if it isn’t first ignited. Even gasoline, which is far more flammable than a candle, does not burn in the presence of oxygen unless it is ignited. In the case of gasoline, the ignition may even be the heat in the air.
Let us recall that in the second stage of photosynthesis, carbon dioxide is combined with hydrogen to form matter. In combustion, that matter is oxidized, that is, it is combined with oxygen O2 to form carbon dioxide CO2 and water, releasing energy or heat in the process. The energy that is released, shall we say, is the very energy that a plant had previously obtained from the sun and has been amassed in the fossil fuel, be it coal, wood, oil or natural gas.
The Fuel
This is any substance that reacts with oxygen in the air, releasing light and heat. In this way, fire is the process by which matter releases its energy or becomes energy. Whatever the substance, it is always the result of a past photosynthesis. Fuel is amassed or stored up energy, it is matter that can transform into energy, back into something it once was. All it needs is a start, a starter engine, and the presence of an oxidizer which is oxygen.
For much of human history, fuels were from plants, alcohol, vegetable oils such as castor oil, and animal fats. During the first industrial revolution, the first fossil fuel came into use – mineral coal – which for a long time had fed the first man-built engine: the steam engine.
Then came petroleum and its derivatives, diesel, kerosene, and gasoline; also natural gas, first for domestic use, later for industrial use. Finally, nuclear energy emerged, resulted from the fission of uranium atoms, releasing energy that is then harnessed by the principle of the steam engine to move electric generators.
The Oxidizer
We have said that most of the fuels are of organic origin. The same can be said of the oxidizing agent, oxygen. As we have seen in speaking about photosynthesis, oxygen is a component of water; there is no free oxygen in space; what little there is, it is part of the water molecule and exists in space as ice. The same thing happens on Earth: oxygen is in the water and the water is in the sea.
In order to release oxygen from water, we need a source of energy to break water molecules by the process of electrolysis. However, this process does not happen in nature – the natural process from which oxygen is released is by photolysis which occurs in the first stage of this process.
It is plants, both terrestrial and aquatic, that release oxygen into the air when they photosynthesize. If our air is currently composed of 21% oxygen which allows and facilitates all the combustion taking place on our planet, both the active ones without as well as the slow ones within all living beings including plants, we owe it all to the cyanobacteria that have been making oxygen at the bottom of the oceans for millions of years, bubble after bubble, with the help of the sun.
The Ignition
Like we have said earlier, a fuel in the presence of the oxidizer does not burn if it is not ignited. There must be a kick-start. Even our universe needed a starter, and its kick-start was the Big Bang. All combustion reactions need to be started; after that everything progresses automatically. Like the domino tiles placed upright one after the other, the tiles will not fall sequentially without a tipping force on the first tile to initiate the chain reaction.
Ignition can be defined as the minimum temperature at which a fuel begins to burn incessantly. In the early days of mankind, when fire was first discovered, ignition was triggered by the friction between two sticks of wood until a spark occurred. Today all combustion reactions are initiated by an electrical spark or a match. Gasoline engines need a spark to initiate the chain reaction; in diesel engines, the diesel is heated and compressed until it explodes on its own.
The Discovery of Fire
Fire is an active combustion in which and by which substances called fuels are combined with oxygen in the air, producing light, heat and carbon dioxide. The technically correct definition, however, does not fully satisfy our amazement and willingness to understand it. We can’t help but be intrigued with this reality. As if by magical arts, it seems to be present everywhere; when invoked or summoned, it becomes visible and cannot be ignored because it burns, destroys, warms, modifies, melts, and then disappears. Nothing remains as it was, it destroys some realities and creates others, before disappearing again and becoming invisible until summoned or invoked again. Fire and its true nature have always intrigued the human beings. Let us see how the Greek mythology treated this reality.
Prometheus Stole the Fire from the gods
In the Greek mythology, it was the Titan Prometheus, with the condescension of Zeus, who created human beings that should have been obedient to the gods. Always benevolent to his creatures, Prometheus climbed Mount Olympus to steal the fire from the gods in order to provide the humans with the best weapon to master nature.
The human civilization progressed rapidly after that, and this displeased Zeus greatly who punished Prometheus by having him chained to a rock. Every day an eagle sent by Zeus came to eat the Titan’s liver, which re-grew every night only to be eaten again by the eagle on the following day. Despite his agony, Prometheus never repented of his rebellious act and was eventually freed from his torment many years later by the demigod, Hercules who was renowned for his strength.
In this myth, Prometheus is exalted for his intelligence, and more important than strength, for his altruism as the benefactor of humanity, for the risk he took and that despite so much suffering, he did not regret what he did for humanity. The progress of mankind is owed to the fact that man is as creative as God. But even with his creativity, he needed fire in order to truly master nature; with fire, man can blend the existing elements and create new ones. Without fire, he would remain in the darkness of ignorance.
It is impossible not to see in Prometheus certain similarities with Christ of the Christian religion. He represents great resources, notably his remarkable intelligence and prudence, but he also follows the idea of rebellion against established power, the liberation of the oppressed, the sacrifice of self without counting the cost, and finally the creation of a new system to which all have access: the Kingdom of God.
The Fireplace
Fire has not only allowed us to associate and mix elements of different nature, like the fusing of metals and the invention of new stronger alloys, but it has also attracted human beings to gather around it and form communities. The need to stay warm, not to die of cold by being excluded from the fire or from the community, led humans to overcome individualism and to create cohesive communities.
This is the reason why the fireplace evokes in us the fraternal feelings of harmony, peace and love; until very recently, the families of a village were counted by fires: the number of fires of a village was the number of families in the village.
Even today, love is symbolically represented as a fire in countless poems. There is a sonnet by the Portuguese poet Camões that attests to this use of fire as a symbol of love: “Love is a fire that burns yet burns unseen.” In fact, love unites two different people, creates bond, conquer individualism, creates equality between people, and creates alliances, harmony, and fraternal coexistence.
For thousands of years, around the campfire, culture circulated and were handed down by oral tradition: grandparents passed on to their children and grandchildren what they themselves had received from their own parents… Winters were long and longer still were the nights; during the day there was no time for coexistence as it was necessary to fight for life. So beckoning is the fireplace, the reminiscent of our ancestral life, that today there are television channels that broadcast a lit fireplace 24 hours every day!
Fire and Civilization
It was the mastering of fire that helped human beings pass from the Stone Age to the Metal Age. It is true that humans have already seen fire in the volcanoes, or a fire caused by the lightning in a thunderstorm, but they did not know how to invoke it, how to provoke it. The mastering of fire was important to create the first objects of clay and metal. Fire in the preparation of food gave man access to new sources of protein, an improved diet and better absorption of food.
For centuries, the fire remained trapped in the bonfire or in the forge of metals and in the potter’s oven. With the industrial revolution, an engine that functioned like a furnace was invented, which boiled water from which steam would exit to move the pistons that drove the wheels of a locomotive. From here to the propulsion engines, cars, ships, airplanes, rockets, was a short step.
We can read the history of human civilization as the history of fire and its use. Finally, we have the nuclear energy which transforms the heat released by the fission or the splitting of atoms and transmitted to water into mechanical energy to move the electric generator, producer of electricity.
The Genesis of Life
What is the origin of life on Earth? How did inorganic matter become organic matter? How did inanimate atoms and molecules transform into animate matter? Abiogenesis is the science that studies this transition. So far, there have been many theories proposed to explain how inorganic inert matter becomes organic living matter, but none without empirical evidence. That is to say, so far no one has managed to create life in a laboratory from inorganic matter.
The first living being or organism that appeared on our planet was a cell without nucleus, therefore prokaryotic, and without membrane. It appeared 4 billion years ago and is therefore almost as old as our planet which was formed 4.5 billion years ago. These bacteria were the archaea and cyanobacteria that began to carry out photosynthesis and paved the way for other life forms.
Later on, somehow, these cyanobacteria were associated, forming eukaryotic cells with nucleus, reducing the cyanobacteria to the chloroplast of these cells. Cyanobacteria still exist, they predate plants and animals, not being one nor the other; but is at the origin of two life forms: plant and animal.
Contrary to what seems logical, animals, not plants, were the first to leave the sea and populate the land. But if the animals were the first, what did they eat on land since there was nothing at the time? The animals were amphibians and they lived most of their life in the sea, but probably came on land to escape their predators or to lay eggs. However, it is known that the algae colonized the coastal rocks 1.2 billion years ago. Animals were the first to come ashore, but plants were the first to establish above water.
Even though cyanobacteria are also known as “blue-green algae”, they are strictly speaking not algae as the latter are restricted to eukaryotes, they are rather photosynthetic prokaryotes, the only prokaryotes able to produce oxygen.
Combustion and Respiration
Since combustion is the process by which combustible materials are oxidized with a release of energy and carbon dioxide, then, similarly, respiration consists of the oxidation of foods like glucose, amino acids and fatty acids, resulting in the production of energy and carbon dioxide. Until now there is no difference between the two, but in respiration not only is energy formed, other products are also formed, that is, more matter. This is why it is called metabolism, that is, a change or transformation.
Broadly speaking, this would be the only difference. However, if combustion instead of being complete is incomplete, that is, instead of being rapid it is a slow combustion, matter is also obtained, as in the case of respiration or metabolism. Think about how charcoal is made from wood: one places all the wood together in a pyre and cover the pyre with soil, leaving only one hole at the bottom and another at the top of the pyre. The wood burns in slow combustion because we limit the entry of oxygen and after a few days, we have all the wood turned into charcoal. If the oxygen was not limited, we would get ashes instead in no time.
The same is true of a long distance runner: if after the first minutes of running, on feeling tired from the increased heart rate, the athlete begins to breathe through his mouth and does not limit the oxygen intake, he will quickly tire and after spending all the glucose, he’ll have to stop. However, if he limits his intake of oxygen, he will force his body to change the fuel, so that instead of using glucose which burns rapidly and consumes a lot of oxygen, he will start to burn fatty acids which burn without the help of oxygen. In this way, he can run for a long time without altering his breathing or heart rate.
Another physical process of slow combustion is the degradation and rusting of metals, iron in particular. Over time, all objects containing iron, and there are many of them since iron is the most widely used metal, and even steel which is said to be stainless but under certain humid conditions, end up oxidizing, that is, burning or degrading due to the presence of oxygen.
Respiration or the Breakdown of Glucose
Glucose is the most widely used fuel inside living beings; the breakdown of glucose releases the energy that is contained in its chemical bonds. Glucose has 6 carbon, 12 hydrogen and 6 oxygen atoms, and in each bond between atoms there is an energy content. As glucose decomposes, energy is liberated and used by the body. Respiration completely breaks down glucose, turning it into energy and inorganic matter, such as carbon dioxide. There is yet another process that breaks down glucose, but only partially, since it transforms it into other organic products; this process is called fermentation.
Metabolism
According to the definition found in the dictionary, metabolism is the set of transformation that chemical substances undergo inside living organisms. It is these reactions that allow a cell or a system to turn food into energy, which will be used by the cells so they can multiply, grow and carry out their functions.
Metabolism is divided into two stages: catabolism (where there is degradation or breakdown of compounds) and anabolism (where there is the synthesis or formation of compounds). Let us recall that photosynthesis is also a two-stage process, and that the second stage cannot take place without the first. The process of making glucose and the process of its degradation, breakdown or decomposition, are similar.
Photosynthesis, which makes glucose from smaller molecules, is an anabolic constructive pathway; cellular respiration or metabolism, on the other hand, where glucose is broken down into smaller molecules, is a catabolic degradative pathway.
We have seen that in photosynthesis plants make their own food and part of it is used for their own consumption. The making of the food is photosynthesis; its use for self-consumption and growth is metabolism. Therefore, the plant cell is in some way more complex than the animal cell; it has a unique organelle that is lacking in animal cells: the chloroplast, through which it carries out photosynthesis. On the other hand, like the animal cells, it has the mitochondria by which it performs metabolism.
In metabolism, the anabolic phase of the cell uses glucose to construct cellular elements, to replace them when they are damaged or aged, and also for growth. In the catabolic phase, energy is released that maintains the constant temperature of the organism and the general functioning of all the tasks of the same organism.
Metabolism is a controlled combustion and it is not possible without the use of oxygen. In this combustion, the fuel is the proteins, fats and carbohydrates which, combined with oxygen in the air from respiration, produces energy which is used for the general functioning of the body, but is also partly stored for later use, and for the growth of the body. Everything in the universe obeys these same laws, functions in the same or in an analogous way.
In conclusion, if the plant life photosynthesis uses energy to make matter, the animal life metabolism burns that matter to make energy. Animal life metabolism as well as all man-made engines work under the same three principles.
Fr. Jorge Amaro, IMC
No comments:
Post a Comment