Meaning of Carbon

All life on earth is based on carbon. But why?

Let's look at some facts about carbon before we actually answer the question stated above. The chemical symbol for carbon is the capital letter, C. The atomic number for carbon is six. Its atomic weight is 12.11. Usually carbon is found in combination with other elements as in carbon dioxide, limestone, coal, and petroleum. Only less than one percent (0.32%) of the earth's atmosphere and 0.2% of the earth's crust are carbon. However, it is this rare element that makes the basis of all living things on earth.

Carbon has significant meaning to lives because its molecular structure, which determines its diverse function. It is capable of making such diverse compounds because carbon can bond to four other groups around it, and to other carbon molecules. For this reason it can form long chain molecules, each with different properties. This allows very long chains of complex molecules to form that are specific enough in their functions, shapes, and binding properties that can enable living organisms to do many things. Even at 30 carbons, there are millions of ways in which the molecule can be arranged. Also, carbon readily forms bonds with many other molecules: hydrogen, oxygen, halogens... and even some metals!

Pure carbon only exists in three forms: diamonds, graphite, and carbon black (charcoal, for example). However,  almost all living things on earth is comprised of carbon. That includes human beings, plants, and animals. Like all animals, humans have a metabolic need for carbon. We get it by eating carbohydrates which are produced in plants during photosynthesis, when carbon dioxide combines with water. Because carbon is so intrinsic to all forms of life, the study of organic carbon compounds is a primary emphasis of organic chemistry.

Forms of Carbon

Silicon (though it is not as abundant) is capable of forming the same sorts of bonds and structures, but opinion is divided on whether silicon-based life forms are a realistic prospect. In part because it needs higher energies to form them, and also because whereas carbon dioxide (one of the main by-products of respiration, a process essential to all known life) is a gas and therefore easy to remove from the body, its counterpart silicon dioxide (silica) has an inconveniently high melting point, posing a serious waste disposal problem for any would-be silicon-based life form. In addition, because silicon has one more layer of electrons than carbon, which means that the attraction of nucleus to electrons is weaker, making the bonding between silicon and other molecules weaker. 

The field of organic chemistry is just the study that based on carbon. The compounds carbon forms with metals are generally considered inorganic. Chains and rings are fundamental to the way carbon-based life forms, that is, all known life forms build themselves. 

Carbon has quite a few industrial uses as well. First and foremost, carbon is the key ingredient in fossil fuels. Carbon in filters absorbs impurities. It is found in carbon paper, paint, and ink. Carbon, added to tires, helps them to wear evenly so they last longer. Finally, by measuring the ratio of carbon to nitrogen and by measuring the amount of carbon-14 that remains in a piece of organic material such as a fossil or a piece of wood, scientists can get a good idea of the age of an item.