Organic compounds are substances that contain carbon (a nonmetallic element that occurs in all plants and animals). All living things have an essential dependence on organic compounds, since carbon occurs in almost every chemical compound found in living things. There are four main types of organic compounds in living things: carbohydrates, proteins, lipids, and nucleic acids.
An organic compound is a combination of carbon and almost any other element. Because of its unique atomic structure (the way a single atom of carbon is built), a carbon atom is able to link up with as many as four other atoms of another element. Since it can also link up with other carbon atoms and form long, stable chains, the variety of combinations carbon can form with other elements is almost limitless. Scientists have already identified more than 1,000,000 organic compounds.
Until the nineteenth century, it was commonly believed that organic compounds only could be produced by something that was living. In those days, it was thought that some sort of "vital force" existed only in living things, and that it was this force that made living things uniquely capable of producing organic compounds. Two hundred years ago, organic meant "vital," or "living." Therefore, in the past, an organic compound was the tissue or the remains of a living thing, while an inorganic compound was something lifeless like a rock or the waters of the earth.
In 1828 the German chemist Friedrich Wohler (1800–1882) changed all of this thinking. That year, he quite unintentionally produced urea, an organic substance formed naturally in the bodies of mammals, in his laboratory using strictly inorganic substances. Starting with this laboratory breakthrough, science eventually came to recognize that no "vital force" was necessary for a substance to be considered an organic compound. Eventually, it was learned that what was important was molecular structure, or the way the atoms arranged themselves into molecules. This led to the modern definition of what became the study of organic chemistry—the chemistry of carbon compounds.
Today, it is known that all living things are not only organic compounds, but that they also are critically dependent on organic compounds. Specifically, foods are all organic compounds since they are made up of carbohydrates, fats, and proteins. Materials such as the cotton and wool in clothing, the petroleum for cars and factories, and all synthetic (man-made) drugs and plastics are organic compounds. Finally, the very chemistry that carries our genetic information—nucleic acids—are complex organic compounds made up of small molecules called nucleotides.
Interestingly, the word organic has been taking on more of its much older (and less precise) meaning, as people now speak positively of the benefits of "organic gardening," "organic food," and "organic vitamins." This use of the term organic suggests that some sort of mysterious "vital" force is at work in these compounds that gives them special qualities that synthetic products do not have. While an organic tomato harvested from a small farm may taste much better than one grown commercially and picked green, from a chemical standpoint, however, they are identical.