"The Design in Oxygen"

By Harun Yahya

Green plants get their energy from the sun through the process of photosynthesis. For the rest of the living creatures of Earth, and that includes us, the only source of energy is a process called "oxidation" which is a fancy word for "burning". The energy of oxygen-breathing organisms is derived from burning the nourishment that they get from plants and animals. As you may guess from the term "oxidation", this burning is a chemical reaction in which substances are oxidized–that is, they are combined with oxygen. This is why oxygen is as vitally important to life as are carbon and hydrogen.

A generalized formula for "burning" (oxidation) looks like this:

Carbon compound + oxygen > water + carbon dioxide + energy

What this means is that when carbon compounds and oxygen are combined (under the proper conditions) a reaction takes place that generates water and carbon dioxide and releases a considerable amount of energy. This reaction takes place most readily in hydrocarbons (compounds of hydrogen and carbon). Glucose (a sugar and also a hydrocarbon) is what is constantly being burned in your body to keep it supplied with energy.

Now as it happens, the elements of hydrogen and carbon that make up hydrocarbons are the ones most suitable for oxidation to take place. Among all other atoms, hydrogen combines with oxygen the most readily and releases the most energy in the process. If you need a fuel to burn in oxygen, you can't do better than hydrogen. From the standpoint of its value as a fuel, carbon ranks third after hydrogen and boron. In "The Fitness of the Environment", Lawrence Henderson comments on the extraordinary fitness that is involved here:

The very chemical changes, which for so many other reasons seem to be best fitted to become the processes of physiology, turn out to be the very ones which can divert the greatest flood of energy into the stream of life. [i]

The Design in Fire (Or Why You Don't Just Burst Into Flames)

The fundamental reaction that releases the energy necessary for the survival of oxygen-breathing organisms is the oxidation of hydrocarbons. But this simple fact raises a troubling question: If our bodies are made up essentially of hydrocarbons, why aren't they also oxidized? Putting it another way, why don't we just go up in flames, like a match that's been struck?

Our bodies are constantly in contact with the oxygen of the air and yet they don't oxidize: they don't catch fire.

The reason for this seeming paradox is that, under normal conditions of temperature and pressure, the molecular (O₂) form of oxygen has a substantial degree of inertness or "nobility". (In the sense that chemists use the term, "nobility" is the reluctance (or inability) of a substance to enter into chemical reactions with other substances.) But this raises another question: If molecular oxygen is so "noble" as to avoid incinerating us, how is this same molecule made to enter into chemical reactions inside our bodies?

The answer to this question, which perplexed chemists as early as the mid 19th century, did not become known until the second half of the 20th century, when biochemical researchers discovered the existence of enzymes in the human body whose only function was to force the O₂ in the atmosphere to enter into chemical reactions. As a result of a series of extremely complex steps, these enzymes utilize atoms of iron and copper in our bodies as catalysts. A catalyst is a substance that initiates a chemical reaction and allows it to proceed under different conditions (such as lower temperature etc) than would otherwise be possible. [ii]

In other words, there is a very interesting situation here: Oxygen is what supports oxidation and combustion and normally one would expect it to burn us up too. To prevent this, the molecular O₂ form of oxygen that exists in the atmosphere has been given a strong element of chemical nobility. That is, it doesn't enter into reactions easily. But, on the other hand, our bodies depend upon the oxidizing property of oxygen for their energy and for that reason, our cells have been fitted out with an extremely complex enzyme system that makes this noble gas extremely reactive.

The Ideal Solubility of Oxygen

The utilization of oxygen by the body is highly dependent upon the property of this gas to dissolve in water. The oxygen that enters our lungs when we inhale is immediately dissolved into the blood. The protein called haemoglobin captures these oxygen molecules and carries them to the other cells of the body where, thanks to the special enzyme system described above, the oxygen is used to oxidize carbon compounds called ATP to release their energy.

All complex organisms derive their energy in this way. However the operation of this system is especially dependent upon the solubility of oxygen. If oxygen were not sufficiently soluble, not enough oxygen would enter the bloodstream and cells would not be able to generate the energy they require; if oxygen were too soluble on the other hand, there would be an excess of oxygen in the blood resulting in a condition known as oxygen toxicity.

The difference in the water-solubility of different gases varies by as much as a factor of a million. That is, the most soluble gas is a million times more soluble in water than the least soluble gas is and there are hardly any gases at all whose solubilities are identical. Carbon dioxide is about twenty times more soluble in water than oxygen is for example. Among the vast range of potential solubilities however, the one possessed by oxygen is precisely what it needs to be for it to be fit for human life.

What would happen if the water-solubility rate of oxygen were different: a little more or a little less?

Let us take a look at the first situation. If oxygen were less soluble in water (and thus also in blood) less oxygen would enter the bloodstream and the body's cells would be starved of oxygen. This would make life much more difficult for metabolically active organisms such as human beings. No matter how hard you worked at breathing, you would constantly be faced with the danger of suffocation because not enough oxygen was reaching your body's cells.

If the water-solubility of oxygen were higher on the other hand, you would be confronted by the threat of oxygen toxicity, mentioned briefly above. Oxygen is, in fact, a rather dangerous substance: if an organism gets too much of it, the result can be fatal. Some of the oxygen in the blood enters into a chemical reaction with the blood's water. If the amount of dissolved oxygen becomes too high, the result is the production of highly reactive and damaging by-products. One of the functions of the complex system of blood enzymes is to prevent this from happening. But if the amount of dissolved oxygen becomes too high, the enzymes cannot do their job. As a result, every breath we take would poison us a little bit more leading quickly to death. The chemist Irwin Fridovich comments on this issue:

All respiring organisms are caught in a cruel trap. The very oxygen which supports their lives is toxic to them and they survive precariously, only by virtue of elaborate defence mechanisms. [iii]

What saves us from this trap–from being poisoned by too much oxygen or from being suffocated by not enough of it–is the fact that oxygen's solubility and the body's complex enzymatic system have been carefully designed and created to be what they need to be. To put it more explicitly, Allah has created not only the air we breathe but also the systems that make it possible to use that air in perfect harmony with one another.

References

[i] Henderson, Lawrence (1958). “The Fitness of the Environment”. Beacon Press, Boston. p. 247-48.

[ii] Ingraham, L.L Enzymic. Activation of Oxygen. In M.Florkin & E.H. Stotz,(Eds.), “Comprehensive Biochemistry: Vol.14” (pp. 424). Elsevier.

[iii] Fridovich, Irwin (1976). Oxygen Radicals, Hydrogen Peroxide, and Oxygen Toxicity. In W.A. Pryor (Ed.), Free Radicals in Biology, (pp.239-240). Academic Press, New York.

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