Water and Life

It is often said that the human body is made up of about 70% of water. It should be specified that the percentage mentioned is the percentage by weight. I try to clarify the concept that I would like to express with a simple example. The human body (but the same applies to any other living being) consists of water molecules, inorganic molecules (iron, phosphorus, calcium, potassium, etc.) and organic molecules (carbohydrates, fats, proteins, etc.). ). The amount by weight of inorganic substances is negligible while the organic substances make up about 30% by weight (in trees with woody trunk this percentage can rise even more than 60% but for the continuation of the reasoning little changes).From a rough estimate I found that on average an organic molecule weighs about 400 times more than one molecule of water (I have not made a calculation too precise because it is useless for the purposes of the reasoning I want to do). To make an analogy, if we compare a molecule of water with a grain of sand of about 1 mm3 of volume and about 3 milligrams of weight, a stone compared to an organic molecule on average should have a volume of about 4 cm3 and weigh about 12 grams. Imagine taking a vessel (which in the analogy represents our human body) and filling it with 700 grams of sand and 300 grams of stones. The question is as follows: How many grains of sand and how many stones are contained in the vessel? An initial answer is: 233,000 sand grains and 25 stones. A second answer is: 99.99% are grains of sand and 0.01% are stones.Well, in the case of the human body we can say exactly the same thing: 99.99% are water molecules and the remaining 0.01% is made up of organic molecules; with the difference that the water molecule is unique while the organic molecules are multiple.Anyone who approaches chemistry knows that the number of molecules involved and not their percentage by weight is important. The first question that arises spontaneously is: if we are so “diluted”, why are not we “puddles”? For example, sea water, although much less diluted than our body is liquid.From these considerations on understands the importance of water in the human body and, more generally, in living beings. It is therefore a question of better investigating the role played by water.

Turin (Italy)

Gianfranco Pellegrini


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